Revised and Enlarged, jd Edition, 6th Thousand. 



ELECTRICITY 



AND ITS 



if? 

RECENT APPLICATIONS. 



v- f f 



A PRACTICAL TREATISE FOR STUDENTS AND 

A MA TE UR S WI TH AN ILL US TRA TED 

DICTIONARY OF ELECTRICAL 

TERMS AND PHRASES. 



BY 

EDWARD TREVERT 

Author of: "Everybody's Hand-Book of Electricity," "How tc 

Make Electric Batteries at Home," " Experimental 

Electricity," " Dynamos and Electric Motors/' 

Etc., Etc., Etc. 



& 


ILLUSTRATED 







LYNN, MASS.; 
BUBIER PUBLISHING COMPANY. 

IQ02 



THE LIBRARY OF 

CONGRESS, 
One Copy Rkwvio 

APR. 22 1902 

ICLASS^- XXi. N* 
COPY B. 



Copyrighted By 

Bubier Publishing Co. 

i 891 

Copyrighted By 

Bubier Publishing Co, 

1902 



,: 




^ 

^ 



PREFACE. 



Although, at the present time) there are a large 
number of valuable treatises orx .the .subject of elec- 
tricity, still there seems to be a demand for more 
information, relating especiaWy-te^th^ practical part of 
this science, and this demand is particularly among 
amateurs and students. For this reason I add this one 
to the list, trusting that it may be as favorably received 
as were my others. As in former books I have in this 
volume avoided technicality as far as possible, and 
confined myself to facts rather than theory. 

I am indebted to The Electrical World, The Elec- 
trical Review, The Electrical Engineer, The Electrical 
Age and the Western Electrician for many articles and 
illustrations furnished by them for this book. I am 
also under obligations to the various electrical com- 
panies and to many individual electricians for informa- 
tion furnished on the subject for this work. 

EDWARD TREVERT. 

Lynn, Mass., June ist, 1891. 



PREFACE TO THIRD EDITION. 

(sixth thousand.) 



By request of the publishers I have revised this book 
and brought it up to date. Quite a number of changes 
have been made, together with some additions, which I 
trust will add to the value of the book. 

Edward Trevert. 

Lynn, Mass., 1902c 



CONTENTS 



CHAPTER 

I. 

II. 

III. 

IV. 

V. 

VI. 

VII. 

VIII. 

IX. 

X. 

XI. 

XII. 

XIII. 

XIV. 

XV. 

XVI. 

XVII. 

XVIII. 

XIX. 

XX. 
XXI. 

XXII. 
XXIII. 



XXIV. 



PAGE 

Electricity and Magnetism 7 

Voltaic Batteries 25 

Dynamos and How to Build One ..... 48 

The Electric Arc and the Arc Lamp . . 98 

Electric Motors and How to Build One, 117 

Field Magnets 146 

Armatures 154 

The Telegraph and Telephone iQk_ ~ 

Electric Bells : How Made, How Used . 1S2 

How to Make an Induction Coil .... 190 

The Incandescent Lamp ~ 199 

Electrical Mining Apparatus . . . . . 209 

The Modern Electric Railway 223 

Wireless Telegraphy 240 

X-Rays 245 

The Electric Fountain 253 

Electro-Magnetic Surgery 256 

Electric Welding 260 

Some Miscellaneous Electrical Inventions 

of the Present Day 264 

Electro-Plating 272 

Electric Gas-Lighting Apparatus . . . . 275 

Electrical Measurement 294 

Resistance and Weight Table for Cotton 

and Silk. Covered and Bare Copper 

W^ire 32S 

Illustrated Dictionary of Electrical 

Terms and Phrases ^^2> 

Appendix. Automobiles 347 



ELECTRICITY 

AND ITS 

RECENT APPLICATIONS 



CHAPTER I. 

ELECTRICITY AND MAGNETISM. 

Electricity and magnetism are very closely 
related. 

What is magnetism ? What is electricity ? 
These are questions that none have yet been able 
to answer. When were they discovered ? To 
answer that question : The Greeks discovered that 
there was a certain force in amber after it had been 
rubbed, and that it would attract small particles or 
light bodies. This substance they called elektron, 
from which came the word electricity. 

The discovery of magnetism has never been 
decided. It is claimed to have been discovered by 
the Greeks, and it is also asserted that the Chinese 
knew of the compass at a much earlier date, yet to 
the Greeks we owe the name of this science. But 
let us pass over this early history as quickly as 
possible. About the year 1600, Dr. Gilbert, first 



ELECTRICITY AND ITS 



physician to Queen Elizabeth of England, published 
his work entitled "De Magnete" and showed among 
many other things that magnetic attraction was 
only peculiar to a few bodies, while electricity was 
universal. 

Among others who made some remarkable dis- 
coveries at this early stage were Volta, Galvani, 
Franklin, Faraday, Ampere and Oersted. Modern 
discoveries in electricity may be said to date from 




\^V:% i^SSHS&^fr^i^i^ 



Figure i. 



the inventions of Barlow, Henry, Jacobi Paci- 
notti, Elias, Froment, Page, Cook, Gaston Plante, 
and Morse, down to the present time, and the 
inventions of Bell, Thomas Edison and Elihu 



RECENT APPLICATIONS. 



Thomson. Every magnet is supposed to have what 
are termed lines of force running around it and 
through it, or to possess what is termed a magnetic 
field. The same may be said of a helix carrying an 
electric current. A very simple experiment to 
illustrate this theory is to lay a piece of paper or 
glass over a bar magnet, and then to sprinkle 
iron filings over the paper or glass. The iron filings 
will be found to have arranged themselves into 
lines. See Fig. i. 







s* 1 y 






Figure 2. 



These lines show the lines of force around the 
magnet. Each particle of the iron filings becomes 



10 ELECTKICITY AKD ITS 

a separate magnet by induction so long as it re- 
mains in the magnetic field. 

The filings should be very small and light, and 
should first be sifted through a very fine sieve. 
When paper is used you should tap it lightly when 
sprinkling the filings. Should one end or pole of 
the magnet be placed next to the paper or glass, 
the filings will arrange themselves as shown in 
figure 2. 

We see by these experiments that the space 
around a magnet is pervaded with this unseen force, 
or lines of force as they are termed. An electro- 
magnet is a magnet which is only magnetic when 
a current of electricity is passing through its coils, 
and is generally made of a core of soft iron with a 
number of turns of insulated wire wound around it. 
This magnet has lines of force like the perma- 
nent magnet. Faraday showed that if the lines 
of force of a magnet were broken by plunging or 
revolving another magnet within its field, that a 
current of electricity was produced in the wire of 
the second magnet. See Fig. 3. 

This is called induction, and it is the fundamental 
principle of the dynamo. 

Should you take a common compass, hold above 
it and parallel to its needle, a wire carrying a 
current of electricity, the needle will instantly turn 
aside. 



RECENT APPLICATIONS. 



11 




12 ELECTRICITY AND ITS 

When the current is flowing along the wire above 
the needle from North to South, the North pole of 
the needle will turn towards the East. If the cur- 
rent should be flowing from South to North, the 
needle will be deflected Westward. If you hold 
the wire below the needle the motions will be 
the reverse. Thus you see by this experiment the 
close relation of electricity to magnetism, and the 
first principle of the electric motor. 

Magnetism like electricity may be communicated 
from one body to another, and as in the case of 
hardened steel, it will be found to remain in the 
article so magnetized, after the magnetic body has 
been removed. In other words the second body 
becomes a magnet like the first. This is also 
accomplished without any apparent decrease of 
strength in the first magnet. Steel and nickel 
seem to retain their magnetism, while iron more 
easily and strongly magnetized, loses its magnetism 
almost immediately after the magnetic influence 
has been removed. 

Another strange thing about magnetism is that 
it can be communicated from one body to another 
through layers of glass, paper or wood, placed 
between the magnet and body to be magnetized, 
and that the intervening medium is directly con- 
cerned in this transmission of magnetic force, and 
that medium is the "ether," surrounding all 
molecules of matter. 



RECENT APPLICATIONS. 13 

Magnetism may be obtained from the earth, as 
the earth itself is a great magnet. A very simple 
experiment is to take a steel bar, place it in the 
magnetic meridian, with the north end dipping 
down, and while it is in this position strike it a 
number of hard blows with a wooden mallet, after 
which it will be found to have become magnetized. 

Although Faraday showed by the aid of very 
powerful magnets that almost every substance was 
susceptible to magnetic influence, generally speak- 
ing, some bodies are not magnetic. Such is the case 
with copper, bismuth and antimony. These are 
called diamagnetic bodies ; while such bodies as 
iron, steel and nickel are highly efficient in magnetic 
power. Every magnet has what is termed a North 
and South pole, which can be seen by observation 
of the compass. A very simple experiment to 
illustrate this principle, is to take a small common 
steel sewing needle, and after having magnetized 
it, by bringing it in contact with the poles of a 
permanent, or an electro-magnet, float it in a glass 
of water when it will be seen to take a north and 
south position. To float the needle it will only be 
necessary tc lay it on a thin piece of tissue paper 
and carefully place both paper and needle on top of 
the water, the paper will soon absorb water enough 
to sink to the bottom of the tumbler, leaving the 
needle floating on the surface. It is supposed that 
should you divide a bar magnet into the smallest 



14 ELECTRICITY AND ITS 

molecules possible, each molecule would be a 
separate magnet, endowed with a North and 
a South pole. This may be illustrated by dividing 
a small bar magnet or by magnetizing a darning or 
knitting needle, and breaking it into small pieces, 
when each piece will be found to have become a 
separate magnet. 

There are various ways of magnetizing bodies. 
Should you bring a bar of steel to a red heat and let 
it cool in the magnetic meridian (that is the bar 
should lie in a North and South position) it will be- 
come magnetized. The most powerful magnets 
are made by winding insulated copper wire around 
the steel to be magnetized, and then sending 
through the coils a strong current of electricity. 
You may partially or wholly destroy" the magnetism 
in a steel magnet by rough usage, as hitting it, or 
knocking it about. It will also lose its magnetism 
on being heated to redness. 

In the first part of this chapter the fact was 
mentioned that when amber is rubbed it will 
attract light bodies. 

Dr. Gilbert discovered that not only amber but 
a large number of substances such as glass, sulphur, 
the diamond, etc., possess the same property. This 
is frictional or static electricity. Static electricity 
can be produced in larger quantities by influence or 
frictional machines. The first machine of this 
kind was invented by Otto Guericke and consisted 



KECENT APPLICATIONS. 



15 



of a globe of sulphur being revolved on an axis by 
turning a crank, one hand being held against the 
globe as a rubber. He afterward improved this 
machine by substituting a glass globe in place of 
the sulphur. The two best frictional machines now 
in use are "The Holtz," and "The Topler machines." 
These machines were invented by two German 




THE HOLTZ MACHINE. 



electricians, Holtz and Topler. The Holtz machine, 
of which there are a number of styles, is shown on 
this page. On a wooden base are mounted two 
glass plates ; the rear plate B stationary, and sup- 
ported by three ebonite insulators, two below and 



16 ELECTKICITY AND ITS 

one above ; while the front plate A revolves in the 
direction of the arrow, on a steel shaft, which 
passes through an opening in the centre of the 
plate B f and is attached to the post at M. A is 
mounted on an ebonite hub, attached to a hollow 
shaft of brass, which revolves on the fixed shaft, 
and carries, at the end next the post, a small pul- 
ley, from which a belt extends to the driving wheel, 
which is revolved by a crank with an ebonite 
handle. The relative sizes of the wheel and pulley 
are such as to give the plate four to six revolutions 
for each revolution of the driving wheel, the plates 
of small machines requiring a more rapid revolu- 
tion than those of larger ones. In front of the 
plate A y I of an inch from the glass, are the combs 
Fand Hy attached to a brass core at the centre of 
the ebonite disc M; and the combs K and Z, in- 
sulated by their attachment to ebonite rods pro- 
jecting from the disc My and connected by brass 
rods with the Leyden jars Cand D, and with the 
sliding-rods P and R. These sliding-rods have 
ebonite handles, and terminate in brass balls at 
their inner extremities. 

The plates are of sheet glass, about \ of an inch 
thick ; of good insulating quality, and well coated 
with shellac. The stationary plate B has two 
circular openings called windows, directly opposite 
the combs K and L ; and, on its rear surface, are 
cemented two paper inductors Zand X \ Zextend- 



RECENT APPLICATIONS. 



17 



ing from H to Z, and X from V to K\ and each 
armed with a row of points, projecting into each 
window. 




THE ToPLER MACHINE. 



The Topler machine shown on this page has the 
same general construction as the Holtz ; but, on 
the front surface of the revolving plate, are 
cemented a number of small metal discs, called 

2 



18 ELECTRICITY AND ITS 

carriers ; usually made of tin-foil with raised brass 
centres, which, as the plate revolves, are brought 
into contact with four wire brushes ; two attached 
to the stationary plate, and two to the uninsulated 
combs. In this way the machine is made self 
inciting, as already mentioned. 

The windows, and the rows of points projecting 
into them, used in the Holtz stationary plate, are 
omitted from the stationary plate of the Topler : 
and the paper inductors are made longer, and have 
small tin-foil inductors under them, connected by 
tin-foil strips, with each other and also with the 
two brushes attached to this plate. 

This machine was constructed by Philip Atkin- 
son, and patented April 10, 1883, and December 8, 
1885. The principal points covered by the patents 
are as follows : 

1. The outside coatings of the Leyden jars C 
and D are of sheet brass, nickel plated ; and are 
screwed firmly to the base ; forming cups into 
which the jars fit closely, and are thus held in a 
fixed position ; affording a firm support to the 
parts connected with them, and preventing liability 
to accident or injury to the jars or plates. 

2. The induced current from these outside 
coatings is conveyed down by the brass screws 
which attach them, and along copper wires under- 
neath, to the terminals of the switch S; through 
which, when closed, it passes from one jar to the 



RECENT APPLICATIONS. 19 

other ; but when open, as in the cut, it passes by 
the brass sockets, seen on the edge, which are also 
connected with the terminals, out through the con- 
ducting cords, and a person, or other object, con- 
nected with their outer extremities. As this 
induced current flows simultaneously with the 
direct current from the inside coatings, the switch 
and sliding-rods place it completely under control 
of the operator. 

3. The brush holders, E and F, are attached to 
the plate B, through holes near its edge ; thus 
giving a direct passage to the electricity from the 
carriers on the plate A, where it is generated, 
through the glass, to the tin-foil inductors, repre- 
sented by the dark shade, and the paper inductors 
T and X> represented by the light shade. By 
passing the electric charge through the glass ', inside 
its edge, an insulating margin is interposed between 
the conductors and the edge, thus preventing loss 
from leakage, which is unavoidable when the brush 
holders are attached by clamps or ears on the edge. 

4. The carriers on the plate A are of sheet 
brass, with raised centres, and are nickel plated, 
making them both durable and ornamental. The 
hard nickel surface is not affected by the action of 
the brushes, or the electricity, while tin-foil soon 
becomes defaced : and the carrier, being practically 
one piece, and its entire surface cemented to the 
glass, its raised centre cannot become detached, as 



20 ELECTRICITY AND ITS 

may happen when the centre is put on separately 
over a tin-foil base. 

5. The combs V and K, also i7and L, radiate 
at an angle of 45 degrees to each other, from the 
central disc M, to which they are attached ; so that 
any possibility of error in regard to their position, 
or of displacement, is practically impossible. 

The following improvements may also be 
noticed: 

The base is made of two-inch strips, glued to- 
gether lengthways, and heavy cleats screwed on 
underneath ; giving all the advantages of iron as to 
freedom from warping, with the insulation and 
elegant finish of the wood. The driving wheel is 
of ebonite and the iron casting, on which it is 
mounted, slides in grooves on an iron plate, and 
is moved by the adjusting screw O, to regulate the 
tension of the belt. 

The ebonite insulators, which support the plate 
B y have soft rubber packing, to ease the pressure 
on the glass. 

The conducting rods of the Leyden jars pass 
through ebonite caps with cork attached under- 
neath ; which gives them a fixed vertical position, 
and affords firm support to the sliding-rods and the 
combs connected with them above. 

These machines do not produce a very large 
amount of electricity, therefore are only adapted 
for experimental purposes. 



RECENT APPLICATIONS. 21 

Opposite conditions of electricity attract one 
another, and although electricity cannot flow- 
through glass it can act across it by induction. 
For example : placing a plate of glass between two 
pith balls, one being electrified positively, the 
other negatively, will not interfere with their attract- 
ing or repelling one another, although the electric 
charges cannot pass through the glass. On this 
principle was invented the Leyden jar, and other 
condensers. The Leyden jar was accidentally dis- 
covered by Musschenbroek, and his pupil Cuneus, 
in the town of Leyden, from which it derives its 
name. It usually consists of a glass jar on which 
is pasted two coatings of tin-foil, one on the inside, 
and one on the outside, the coating covering the 
jar, three-fourths of its length. Electric con- 
nection is made by a chain, or a flexible wire 
hanging into the jar from a brass rod, which may be 
supported by a wooden cover to the jar, to which 
the rod is fixed. A brass nob is attached to the 
top of the rod. To charge the jar, it is necessary 
to hold or connect this nob to the prime conductor 
of an electrical machine ; the outer coating being 
either held in the hand, or connected to the earth 
by a wire. The jar can be easily charged in a few 
minutes in this way, and if made of good glass, 
kept dry and free from dirt will retain its charge 
for many hours. The jar may be discharged by 
holding it in one hand by the outer coating and 



22 ELECTRICITY AND ITS 

touching the brass nob by the other hand. The 
person so doing will see a bright spark pass 
between the nob and the hand, making a sharp 
report, and at the same time giving the person a 
convulsive shock. 

A very simple Leyden jar can be made in the 
following manner, and was the original experiment 
of Musschenbroek and his pupil. Take a glass 
Dottle, fill it about two-thirds full of w T ater ; make 
a hole through the cork and push through it a long 
nail, so that it hangs low into the water, when the 
cork is in the bottle. This jar can be charged like 
the modern Leyden jar, and in the same way, the 
water acting as the inner coating and the hand as 
the outer. When the jar is charged, it can be dis- 
charged by holding it in one hand and touching the 
top of the nail with the other. Thin glass has a 
greater capacity as an accumulator, than thick glass, 
but if the glass should be too thin, the jar will be 
liable to be destroyed by the spark of a powerful 
charge actually piercing it. A powerful battery 
may be made of Leyden jars by connecting a num- 
ber of them together by their thin inner coatings : 
then also uniting their outer coatings. Care should 
however be taken in discharging this battery of 
Leyden jars, by using a pair of discharging tongs, 
as a shock from such a battery might prove fatal. 
The discharging tongs is an arrangement consist- 
ing of a brass rod with two brass nobs, and 



RECENT APPLICATIONS. 23 

insulated from the hand by a glass handle. The 
electric discharge we see during a thunder shower 
is this same kind of so called static electricity. 

Electricity is often found in belts, running 
pulleys and shafting in factories. Placing your 
finger, or hand, or what is better, holding a piece of 
copper near a large belt which is running shafting, 
you will hear a cracking sound and sometimes 
receive a perceptible shock. The writer has 
seen enough electricity collected on wires from 
large belts to light coal gas. This experiment is 
more successful in cold weather. Quite a quantity 
of frictional electricity is developed in cylinder 
printing presses when moving at full speed, which 
electrifies the paper so that the sheets will stick 
together quite firmly, and should you pull them 
apart the same crackling sound spoken of in 
regard to the belt is heard, and the person separa- 
ting them will sometimes receive quite a shock. 

Electricity can also be obtained by joining two 
dissimilar metals by soldering, and then heating 
their points of contact. Such currents are called 
Thermo-Electric currents. The same result may 
be obtained by lowering the temperature at the 
point of contact. For example, the metals joined, 
may be copper and iron or Bismuth and Antimony. 
There are a number of other metals which if joined 



24 ELECTRICITY AND ITS 

together in the way here described will produce 
Thermo-Electricity. 

Now let us take up the subject of the production 
of electricity by chemical action, or by voltaic bat- 
teries as they are termedo 



RECENT APPLICATIONS. 25 



CHAPTER II. 

VOLTAIC BATTERIES. 

Voltaic Batteries derive their name from Volta, 
who made the discovery that when a number of 
contacts of two dissimilar metals are placed together 
with some moistened flannel or paper placed 
between each pair, a small amount of electricity 
can be obtained by touching simultaneously the 
top and bottom of the pile of discs, or the wires 
connected to them. This was called the Voltaic 
pile, and was made by placing a pair of discs of 
copper and zinc in contact with one another, then 
laying on the zinc disc a piece of flannel or paper, 
moistened in some salt and water, or very dilute 
sulphuric acid, then another pair of discs of copper 
and zinc and so on, being sure to separate each 
pair of discs by a moist conductor. 

Volta soon improved this by placing in a glass 
jar, partly filled with a very weak solution of sul- 
phuric acid, a strip of copper and a strip of zinc ; a 
wire was soldered to each strip, and by connecting 
a number of these cells, the zinc of one cell to the 
copper of the next and completing the circuit by 



26 ELECTRICITY AND ITS 

bringing the terminals together, a much larger 
quantity of electricity is obtained than from the 
Voltaic pile. But such a battery as this is found 
to be wholly impracticable, polarization taking place 
almost immediately. By polarization, we mean 
that bubbles of hydrogen liberated at the surface of 
the copper plate stick in large numbers on its sur- 
face. This weakens the current by causing a 
resistance to the flow of the current, for these 
bubbles of gas are bad conductors. It also weakens 
the current by setting up an opposing electro- 
motive force, hydrogen being almost as oxidizable 
a substance as zinc. Thus you see the hydrogen 
produces a difference of potential which tends to 
start an opposing current in the opposite direction 
from the zinc to the copper element. In order to 
overcome this polarization various means have been 
devised, viz : 

ist. — Mechanical means can be used by simply 
brushing off the bubbles of hydrogen from the sur- 
face of the positive pole ; thus reducing the resist- 
ance. Another remedy which is employed in 
Snee's Cell, which consists of a zinc and a plati- 
nized silver plate dipping into dilute sulphuric acid. 
The silver plate having its surface thus covered 
with a rough coating of finely divided platinum 
gives up the hydrogen bubbles freely. 

2d. — Chemical means may be used by adding a 
highly-oxidizing substance, such as bichromate of 



RECENT APPLICATIONS 27 

potash, chloride of lime, bichromate of soda, etc., 
which, if added to the acid, destroy the hydrogen 
bubbles, whilst they are in the nascent state. 

3d. — Electro-chemical means may be used, which 
is done by employing double cells. This means is 
used in the Daniels and Gravity cells. In this 
case, solid metal, such as copper, is liberated in- 
stead of hydrogen bubbles which entirely prevents 
polarization. 

All zinc used in batteries should be amalgamated, 
as the impure zinc that is for commercial use will 
continuously dissolve in acid and give off hydrogen 
bubbles, even when the circuit is not closed. This 
is called local action. It is caused by impurities in 
the zinc, such as particles of iron or other metals. 
These particles set up an opposing current, and 
each particle acts as a separate miniature voltaic 
cell. Amalgamation does away with this. The 
particles of impure metal do not dissolve in the 
mercury, but are carried off from the surface of the 
zinc plate by the hydrogen bubbles. As the zinc 
dissolves, a part of the film of mercury unites with 
fresh portions of the zinc, consequently always 
keeping a clean bright surface presented to the 
acid. 

Zincs may be amalgamated in the following 
manner : First, immerse the zincs in a solution of 
dilute sulphuric acid, then into a bath of mercury. 



28 ELECTRICITY AND ITS 

A brush or cloth should be used to rub the mer- 
cury well into the zinc so as to reach all points of 
the surface. 

Electric Batteries may be classified according to 
their use into open circuit and closed circuit bat- 
teries. An open circuit battery is a battery which 
is used when a current is needed for a few seconds 
at a time. If the circuit is kept closed too long 
the battery will become polarized, that is, hydrogen 
will collect on the carbon and prevent the current 
passing through the circuit. If, however, the 
circuit is opened the battery will recover itself in 
time. These batteries are designed for bells, tele- 
phones, gas-lighting work, etc. To this class belong 
the Leclanche, Samson and Champion. 

Closed circuit batteries are used for continuous 
work as for electric lighting, electro-plating, fire 
alarms, etc. To this class belong the Grenet, 
Gravity, Grove, Bunsen, and Fuller Batteries. 

OPEN CIRCUIT BATTERIES. 

The Samson Battery. — This battery is not only 
presented for its great efficiency in call bell, an- 
nunciator, burglar alarm and gas-lighting work, but 
it is also especially adapted to telephone service on 
account of its remarkable endurance and long life. 



RECENT APPLICATIONS. 



29 



The essential characteristics of the Samson 
Battery are its fluted carbon porous cup and cylin- 
drical zinc. 

The carbon cup is corrugated, to present a much 
larger surface to the action of the solution ; is 
porous to render the flow of the solution into the 
cup unresisted ; is filled with a depolarizing 
material, to add to the battery durability and re- 
cuperative power. The zinc is of the best quality, 





ZINC, CARBON AND COVER. 



well amalgamated, presents to the solution an 
unusually large surface, and nearly surrounds the 
carbon cup, thus reducing the internal resistance 
of the battery to almost nothing. 



30 



ELECTRICITY AND ITS 



The neck of the jar has a choke which supports 
a rubber cover, to prevent evaporation, closely fit- 
ting the corrugated carbon, which it holds safely 
apart from the zinc. In this cell the exciting 
liquid is a solution of sal ammoniac. 




COMPLETE CELL OF CHAMPION 
BATTERY. 



CARBON RESERVOIR OF CHAM- 
PION BATTERY. 



Champion Battery. — The accompanying four cuts 
illustrate a new primary, put upon the market by 
Mr. C. J. Hirlimann. 

The battery is made up in two distinct patterns, 
the difference, however, lying only in the form of 



RECENT APPLICATIONS. 



31 



the zinc, and it will be seen by referring to the 
illustrations that one of the zincs consists of the 
ordinary rod Leclanche zinc, while the other is a 
large surface corrugated sheet zinc. 




CORRUGATED ZINC OF CHAMPION 
BATTERY. 



ROD ZINC OF 
CHAMPION 
BATTERY. 



When the rod zinc is employed the battery is 
most suitable for telephone work and where a con- 
stant output of energy is required, while the corru- 
gated zinc is used where large quantities of current 
for a short time is the desideratum, as in gas- 



32 ELECTRICITY AND ITS 

lighting work, electric bell ringing, etc. In further 
support of the merits of the battery an official 
measurement of the cell by the distinguished 
electrician, George dTnfreville, of New York city, 
is submitted, in which the following figures are set 
forth: Electro-motive force, 1.4 volts; internal 
resistance, .17 ohms; current, 8.3 amperes. 

The carbon reservoir is quadrangular in shape, 
and charged with ingredients under a secret 
formula, and is provided with a neat top, fitting 
closely into a glass jar, to prevent evaporation and 
facilitate sealing. 

The exciting liquid is a solution of sal ammoniac. 

The Leclanche Battery. — In this cell the exciting 
liquid is a solution of sal ammoniac. In this the 
zinc dissolves, while ammonia, gas and hydrogen 
are liberated at the carbon pole. 

To prevent polarization in the disque form, the 
carbon plate is packed inside a porous cell with 
fragments of carbon and powdered bifloxide of 
manganese, which slowly yields oxygen, and de- 
stroys the hydrogen bubbles. 

The Leclanche cell will give a continuous current 
only for a short time, the power falling off, owing 
to the accumulation of hydrogen bubbles ; if the 
circuit is left open for a time the cell recovers 
itself, the binoxide gradually destroying the polar- 
ization. 



RECENT APPLICATIONS 



33 



The cell is in other respects perfectly constant, 
very clean, and as it does not require renewing for 
months or years, when closed only for a few 
seconds at a time, it is well adapted for working 
electric bells, annunciators, burglar alarms, and for 
other domestic purposes. This battery is set up 
in the following manner : 





DISQUE FORM. 

Put six ounces of sal-ammoniac into the glass 
jar, fill one-third full of w r ater, and stir. Put in the 
porous cell and fill with water to the neck of the 
jar, pouring a little water into the hole in the 
porous cup. Put in the zinc and connect the 
battery. 

The inside of the rim of the jar is paraffined, and 
should be kept greased to keep the salts from 
creeping. 



34 



ELECTRICITY AND ITS 



The battery should be kept in a dry place of 
medium temperature. It requires very little atten- 
tion ; water should be poured in occasionally to 
supply the loss by evaporation. In case the solu- 
tion becomes milky, and the battery fails to work, 
the solution should be thrown out and fresh sal- 
ammoniac and water put in. If this does no": 
restore the battery, soak the porous cell in warm 
water. If it still fails, new porous cells must be 
used. 



mBHmm i 

^■i' PATENT 

NOV-16, I88C 

■Al6:i-i,is;l|||L„ 

■MfeH.27 - 88. f 




PRTSM FORM. 



The Prism Form. — In this cell the porous cup is 
dispensed with, and in its place is substituted a 
pair of compressed prisms or plaques, which are 
simply attached to the carbons by means of two 
rubber bands. The prisms are formed of a paste 



RECENT APPLICATIONS. 



35 



consisting of 40 parts binoxide of manganese, 52 
parts carbon, 5 parts gum and 3 parts bisulphate of 
potassium. This paste is formed into prisms under 
a pressure of about 4,000 pounds to the square 
inch at the temperature of boiling water. In the 
latest prisms the bisulphate of potassium is omitted. 
When the elements have become exhausted from 
long service the prisms should be taken off, new 
prisms should be attached, and the battery set up 
as before, with new zinc and fresh sal-ammoniac. 




GROVE CELL. 



Close Circtcit Batteries. — The Grove cell consists 
of a glass jar containing the amalgamated zinc 
cylinder and dilute sulphuric acid. In the inner 
porous cup a piece of platinum foil dips into con- 
centrated nitric acid. There is no polarization, for 
the hydrogen liberated at the zinc plate, in passing 
through the nitric acid on its way to the platinum 
pole, decomposes the nitric acid, and is itself 
oxidized, producing water and the red fumes of 
nitric peroxide gas. This gas does not produce 



36 



ELECTRICITY AND ITS 



polarization, as it is readily soluble in nitric acid. 
The battery has both a large amount of electro- 
motive force and a low internal resistance. It will 
furnish continuously for three or four hours a strong 
current. This battery is shown on page 35. 




BUNSEN CELL. 



The Bunsen cell is a modification of the Grove, 
the difference being in this cell that the platinum 
foil is replaced by a plate of hard carbon. 

Gravity Batteries are two fluid cells. 

Instead of employing a porous cell to keep the 



RECENT APPLICATIONS. 



two liquids separate, it is possible, where one of 
the liquids is heavier than the other, to keep the 
latter on the bottom, and have the lighter floating 
upon it ; this s'eparation, however, is never perfect, 
the heavy liquid slowly diffusing upward. 




GRAVITY BATTERY. 



To set up this battery proceed as follows : 
Open out the copper, so as to present all of its 
surface to the action of the solution, place it in the 
bottom of the jar, run the insulated wire out of the 
top of the jar for connecting up. 

Suspend the zinc above the copper by hanging 
the hooked neck on the rim of the glass. 

Pour clean soft water into the jar until it covers 
the zinc, then drop in six or eight ounces of copper 
sulphate (blue vitrol) in small crystals. 



38 



ELECTRICITY AND ITS 



The Edison Lalande Cell. - — The elements em- 
ployed in this battery are zinc, and black oxide 
of copper, in a solution of high grade caustic 
soda. When the circuit is closed, the water 
of the solution is decomposed into nascent oxy- 
gen and hydrogen. The oxygen goes to the 
zinc plate (the negative pole), and unites with 
it, forming oxide of zinc. This, in its turn, is dis- 
solved by the caustic 
soda solution, forming 
zincate of soda. The 
hydrogen goes to the 
oxide of copper plate 
(the positive pole), and 
unites with the oxygen 
contained in the oxide 
of copper, forming water 
(H 2 0), and leaving be- 
hind metallic copper. 
As the oxide plate is 
porous, this action goes 
on, when the battery 
is in service, until the 
oxide plate is reduced throughout its entire 
mass to metallic copper in a finely divided 
state. 

The positive pole is a compressed plate of oxide 
of copper, having the surfaces reduced to metallic 




THE EDISON LALANDE CELL. 



RECENT APPLICATIONS. 39 

copper so as to give good conductivity to the 
battery. 

The negative pole of the battery is made of 
purest zinc, to which mercury is added at the 
time of casting the plates, so that the mercury 
will amalgamate the zinc throughout its entire 
mass, and prevent any local action occurring. 
Each battery contains two zinc plates, the stems 
of which have a small hole punched in the top 
of same. 

The containing vessel is a porcelain jar with a 
porcelain cover fitting on same, both of which are 
made of vitreous porcelain so that they will be 
strong and durable. In charging the battery, it 
is only necessary to fill the jar to the brown line 
on the inside, and then to add the charge of caustic 
soda, which will dissolve almost immediately. 

A layer of oil is used on top of the cells to pre- 
vent creeping and evaporation. 

All Edison-Lalande batteries have an initial 
E.M.F. of .95 volt, which drops to .7 volt on closed 
circuit. They are made in a variety of sizes, each 
adapted to a particular class of work. 

Mesco Dry Battery, — The battery shown in 
the cut is made by filling in the space between 
a hollow carbon cylinder and a metal plate, which 
faces both external and internal surfaces of the 
cylinder, with the chemicals in a dry or rather a 



40 



ELECTRICITY AND ITS 



pasty form. The whole is then sealed tight into 
the covering and is ready for use. Neither of 
the elements is consumed during action, but the 
chemicals are decomposed. Its E. M. F. is about 
two volts, and it will give a current of from 6 
to 10 amperes, as its internal resistance is very 

low. 

The G reiict Battery, 
shown in the engraving, 
consists of a glass jar or 
bottle. A well amalga- 
mated zinc plate forms 
one pole, and a pair of 
carbon plates, one on 
each side of the zinc, 
joined at the hard rub- 
ber top, forms the other 
pole. The zinc plate is 
fized to a brass rod, by 
which it can be drawn 
up out of the solution 
when not in use. To 
charge this battery, pro- 
ceed as follows : 

To three pints of cold 
water add five fluid 
ounces of sulphuric acid. 
When this becomes cold 




D 



|he me. 

^ BATTEL 




RECENT APPLICATIONS. 



±1 



add six ounces (or as much as the solution will 
dissolve) of finely pulverized bichromate of potash. 
Mix well. 

Pour the above solution into the glass cell until 
it nearly reaches the top of the spherical part; 
then draw up the zinc and place the element in the 
cell. The fluid should not quite reach the zinc 
when it is drawn up. 




GRENET BATTERY. 



Storage Batteries or Accumulators. — The possi- 
bility of storing electricity was first suggested in 
1801, by Gautherot's discovery that two plates of 
the same metal immersed in acid, after having 



42 



ELECTRICITY AND ITS 




RECENT APPLICATIONS 



43 




STORAGE CELL. 



44 ELECTRICITY AND ITS 

been subjected to the action of an electric current 
in one direction, would produce a secondary cur- 
rent in the opposite direction. 

In 1859 Gaston Plante, while engaged in a series 
of experiments upon this phenomenon, devised a 
storage battery consisting of plates of lead im- 
mersed in dilute sulphuric acid. 

Camille A. Faure, after many experiments in 
this field, made the remarkable discovery that a 
paste of oxide of lead mechanically applied to the 
plates, brought them instantly into the condition 
to receive a charge, which was only accomplished 
by Plante after months of electrical treatment. 

Should the reader wish to make an experimental 
storage cell he will find complete directions for so 
doing in the author's book of " How to Make 
Electric Batteries at Home." The storage battery 
requires recharging, either by having a current 
sent through it from a direct current dynamo, or a 
number of primary batteries, the current from a 
dynamo being preferable and the least expensive. 
The current is sent from the negative to the posi- 
tive electrodes. The strength of this current 
should be about four volts to a cell, the average 
capacity of the storage cell being two volts. 

The storage cells shown in the illustrations are 
made by The Accumulator Company of New York, 
and combine the invention of Faure with many 
improvements. 



RECENT APPLICATIONS. 



45 



This cell is made up of fifteen plates, eight neg- 
atives and seven positives, and is especially adapted 
to isolated and central station lighting. These 
plates are separated by what is called a hair pin 
separator, which prevents them from short circuit- 
ing or buckling. 




Fig. i 



The electro-motive force of the cell is about 2 
volts. 

The internal resistance is extremely low, say 
from .001 to .005 ohm, and the range of the current 



large. 



The capacity of the cell in perfect condition is 
somewhat underestimated at 300 ampere-hours ; 30 
amperes, a safe working current, will last for over 
ten hours, with not exceeding ten per cent, drop in 



46 



ELECTEICITY AND ITS 



electro-motive force, or a less current will be sup 
plied by the cell for a proportionately greater 
number of hours. A greater rate — up to 300 
amperes — could also be obtained, but so great a 
strain upon this size of cell would injure the plates. 





Fig. 2. 



The illustration on page 42 represents the 
"15m" accumulator elements and hard rubber 
box ; and the illustration on page 43 represents 
the " 23 m " accumulator elements in glass. 

Before closing this chapter perhaps it would be 
well to say something in regard to connecting 
voltaic cells, in order to obtain different results. 
For example, supposing we have a battery of five 
cells, and each cell has a voltage of two volts, and 
gives a current of one ampere, and wish to run an 



RECENT APPLICATIONS, 47 

incandescent lamp that requires ten volts and a 
current of one ampere, we would connect the 
positive pole of the first cell to the negative pole of 
the second, then the positive pole of the second to 
the negative pole of the third, and so on until all 
the cells are connected, then connect the negative 
pole of the first cell and the positive pole of the last 
cell to the two wires of the lamp and we will have 
the required ten volts and one ampere of current. 
This is called connecting in series. See Fig. i. 

Suppose our lamp only required two volts and 
five amperes to run it, and one cell only gave one 
ampere and two volts. We will then have to con- 
nect our batteries in multiple, or, in other words, 
for quantity ; that is, we will connect all the 
positive poles of each battery together, and all the 
negative poles together, then we will take one 
wire from our positive poles and one wire from 
our negative poles and connect them with our 
lamp. See Fig. 2. 



48 ELECTRICITY AND ITS 



CHAPTER III. 

DYNAMOS AND HOW TO BUILD ONE. 

Dynamos, or generators, as they are termed, 
are machines for generating electricity by mechan- 
ical force. Practically any machine that generates 
electricity by mechanical means, from the large 
generators of to-day, back to the copper disc 
which was rotated between the poles of a 
magnet by Faraday, may be called a dynamo. 
We may say that a dynamo consists of three parts, 
namely : The field magnets, the armature and 
the commutator. 

The field magnets are usually the stationary 
part, and consist of iron cores, solidly connected 
together with an iron frame, and have a number of 
layers of insulated copper wire wound around 
them. These magnets are called electro-magnets, 
because they are practically only magnetic when a 
current of electricity is passing through their 
coils. 

There, however, remains a feeble residual 
magnetism in the pole pieces, which, when excited 



RECENT APPLICATIONS. 49 

by rotating the armature at a high rate of speed, 
within the magnetic field, will induce a small 
current in the coils, that rapidly increases, and on 
being transmitted through the coils of the electro- 
magnets, augments their magnetism and produces 
in them still stronger currents. 

The armature, usually the rotating part, is an 
iron core, made up of soft iron discs. These discs 
are mounted on a shaft, and are insulated from one 
another by placing between them thin sheets of 
paper. Upon this core is wound a number of 
layers of insulated copper wire, and their free ends 
connected to the segments of the commutator. 

The commutator consists of a number of copper 
bars or segments, usually affixed radially around 
the shaft of the machine, each segment being 
thoroughly insulated by thin sheets of mica, each 
segment receiving the electricity that is generated 
from the coil or coils attached to it. The commu- 
tator is employed to change the direction of the 
current. 

The current is collected from the commutator 
by brushes. These are either made of coppei 
wires bundled together, copper plates, or carbon 
plates, which are in contact against the com- 
mutator. 

There are two types of dynamos — the continuous 
current and the alternating current. 



50 



ELECTKICITY AND ITS 



In the continuous current dvnamo the current 
generated always flows in the same direction, 
there being a commutator from which the current 
is collected by the brushes. 

In the alternating current machine the current 
generated flows at rapid intervals, first in one and 




Figure i. 



then in the opposite direction. This dynamo 
having no commutator, a collector of two metal 
rings is necessary, on which the brushes rest. 
The magnets of this machine must have a con- 



EECENT APPLICATIONS. 



51 



tinuous current to excite them, and this current is 
generated by another small, continuous current 
machine, which is called the exciter. 

There are three ways of winding dynamos : the 
series, the shunt, and the compound. In the series 
wound dynamo, the generated current is passed 
through the field magnet coils, which are connected 
in series with the armature and external circuit. 
See Fig. i. 



"ooo 






fir* y 


- 






c 




i i 




■■) 




« «v 





Figure 2. 



In the shunt wound dynamo the field magnets 
are wound with fine wire to receive only a small 
portion of the whole current generated in the 
armature. These coils are connected to the 
brushes of the machine and constitute a by-pass 
circuit, or what is called a shunt. See Fig. 2. 



52 



ELECTRICITY AND ITS 



000000000 | 6(!)666 




Figure 3. 

The compound wound dynamo is a combination 
of the series and shunt. The field magnets are 
wound with two sizes of wire : Coarse wire, which 
is in series with the armature and the external 
circuit, and a finer wire, which is in shunt with 
the brushes. See Fig. 3. This dynamo is adapted 
more especially for incandescent lighting. 

To produce a current from a dynamo a certain 
speed of the armature must be obtained, for the 
machine will refuse to magnetize its own magnets 
when there is too much resistance or little speed. 

Thus far we have only looked into the principles 
of the dynamo. Let us now look into some of the 
different systems of the present day. We will 
take first "The Edison." 



RECENT APPLICATIONS. 53 

TJie Edison Direct Ctcrrent Dynamo. — The field 
magnets consist of vertical cylinders with large 
wrought-iron cores, which rest upon cast-iron 
pole pieces, and nearly enclose the armature. The 
armature is drum shaped. The core consists of a 
number of sheet-iron discs, insulated from each 
other by sheets of thin paper. The core is mounted 
on an iron shaft, but insulated from it by an 
interior cylinder of lignum vitae, while an external 
covering of paper insulates it from the coils. The 
coils consist of cotton covered copper wire, 
stretched longitudinally and grouped together in 
parallel, a number of wires in a group, all of the 
group being so connected as to form a continuous 
closed circuit. The groups are arranged in con- 
centric layers, and are of the same number as the 
segments of the commutator, the ends of the wires 
in each group being attached to arms connecting 
with the commutator segments, a spiral arrange- 
ment being adopted in making the connections be- 
tween the straight portions of the wire and the 
arms. The object of grouping is to secure flex- 
ibility for winding by the use of small wire and low 
electrical resistance, by having several wires in 
parallel, the effect as to the resistance being prac- 
tically the same as if the several wires were com- 
bined in one. At the ends the wires are insulated 
from the core by discs of vulcanized fibre with pro- 
jecting teeth. The discs of the core are bolted 



54 



ELECTRICITY AND ITS 



together by insulated rods, and the coils are con- 
fined by brass bands surrounding the armature. 
The brushes are composed of several layers of 
copper wires, combined with flat copper strips, two 




EDISON DIRECT CURRENT DYNAMO. 

layers of wire being placed between each two strips. 
This arrangement is to give a more perfect con- 
nection, and to prevent sparking by furnishing 



RECENT APPLICATIONS. 



55 



numerous points of contact, the copper strips 
confining the wire and making the brush more 
compact. On page 54 will be found an engraving 
of the machine. 




THE WOOD ARC DYNAMO. 

The Wood Arc Dynamo. — The engraving on 
this page gives a very good idea of the size and 
general appearance of the new improved Wood Arc 
Dynamo. 

The armature is of the Gramme type, and is 
made in the form of a ring of soft iron wire. It 
is then closely covered with coils of carefully in- 
sulated copper wire. These coils are so insulated 
and placed in the armature as to prevent the possi- 
bility of a short circuit between them. 



56 ELECTRICITY AND ITS 

The commutator plays an important part in the 
protection of the armature. The narrow copper 
plates of which it is made are thoroughly insulated 
from each other with fire-proof material. It is so 
constructed that one or more of its sections may be 
readily removed, without interfering with the re- 
maining ones. Where the ends of the armature 
coils are connected to the commutator clamps, 
they are enlarged so as to increase their strength 
and lessen their tendency to vibrate or break, and 
these enlarged ends are connected with the radial 
arms of the commutator by a screw clamp. This 
enables any section or coil in either the commu- 
tator or the armature to be easily removed or 
replaced without seriously interfering with any 
other part of the dynamo. 

The centre is composed of a gun-metal spider, so 
constructed as to give perfect ventilation, and the 
greatest strength with the least weight. The 
spider also absorbs any undue heat that may be 
electrically developed in the ring, and this heat is 
so quickly dispersed by the current of air produced 
that the tendency to overheating is entirely re- 
moved. 

The dynamo is placed on a sliding base, which 
renders it possible to tighten or loosen the belt 
while the machine is in operation. 



RECENT APPLICATIONS. 57 

The Thomson-Houston Arc Dynamo is of unique 
construction. It was designed by Professor 
Elihu Thomson and Edwin J. Houston, of Phila- 
delphia. Its armature is nearly spherical, and is 
wound with only three coils. The three coils are 
wound over the shell of the armature in three wind- 
ings, each layer being insulated from the shell and 
its neighbors. When the winding is completed, the 
three ends of the coils are carried through an open- 
ing in the shaft and attached to three segments of 
the commutator. The field magnets are cup shaped ; 
and consist of two cast-iron tubes, furnished at 
their inner ends, with hollow cups cast in one with 
the tubes, and accurately turned to receive the ar- 
mature. 

Upon these tubes are wound the coils ; afterwards 
the two magnets are united by means of a number 
of wrought-iron bars, which constitute the yoke of 
the magnet and at the same time protect the coils. 
The magnets are carried on a framework which also 
supports the bearings for the armature shaft. 

The commutator has only three segments, in con 
tact with which are four brushes. Regulation is ob- 
tained by an electro magnet regulator, which con- 
trols the amount of current by automatic shifting 
of the brushes in such a way that they short cir- 
cuit one of the armature coils for a greater or less 
period of time, as the occasion may require. 

When from a reduction of resistance in the lamp 



58 



EEECTKICITY AND ITS 




RECENT APPLICATIONS. 59 

circuit by the extinguishing of a lamp, or other- 
wise, the current feeding the other lamps becomes 
liable to abnormal increase. This increase of cur- 
rent is made to flow through the coils of wire sur- 
rounding the iron core of the regulator ; the core 
then becomes magnetized, causing the yoke to 
which the brushes are attached to be drawn up 
towards the regulator magnet. This results in 
shifting the brushes on the commutator, so that 
they draw away from the maximum point, decreas- 
ing the potential. When more lights are turned 
on, the reverse action takes place. The current 
governing the regulator is cut in and out by means 
of a pair of electro-magnets, termed the controller 
magnets, connected with the regulator magnet of 
the dynamo. 

Sparking at the commutator is reduced by a 
blower being so placed that it sends a current of 
air directly on to the point of contact of the brushes 
and commutator which blows out the spark. 

The largest machines have an electro-motive 
force of 3000 volts, and will maintain 63 arc lights 
in a single circuit. 

IOOO K. W. TJiree-PJiase Rotary Converters. — 
The rotary converters built by the General Electric 
Company have many of the same features of struc- 
tural detail that distinguish the direct current gen- 
erators of the same make. The external yoke of 



60 



ELECTRICITY AND ITS 




RECENT APPLICATION'S. 61 

the field frame is made of cast iron, and its upper 
half is fastened to the lower half by bolts hidden 
completely within recesses cored in the side sup- 
ports, thus doing away with unsightly pro- 
jections and improving the appearance of the 
machine. The poles also embody the same fea- 
tures as those of the generators, being solid steel 
castings bolted to the yoke ring so that any pole 
can be removed for the repair of its winding with- 
out disturbing the yoke ring. 

The poles have extending tips, which distribute 
the magnetism over a greater number of armature 
teeth and thereby reduce the density, the iron 
losses, and heating in this part of the machine. 
The fields may be shunt or compound wound to 
obtain the desired regulation, and the effect of the 
series coil may be adjusted by a variable shunt 
exactly like that used on direct current generators. 

The armatures are, as a rule, bar wound, upper 
bars being connected to the lower bars by soldered 
clips on the collector ring end of armature. 

Alternating Ctirrent Apparatus. — The most 
important advance that has been made in incan- 
descent lightning from central stations is the 
introduction of the Alternating Current system. 
By its use, the difficulties hitherto experienced 
in long-distance incandescent lighting are com- 
pletely obviated, and it is now possible to fur- 



62 ELECTRICITY AND ITS 

nish a reliable and efficient service over large areas 
from a central source of supply, with an economy 
which will commend the system to any company 
proposing to do an incandescent lighting business. 

The Alternating Current System may be de- 
scribed briefly as one in which is employed a dyna- 
mo machine producing alternately currents of high 
electro-motive force or pressure and transformers 
in which are produced currents of lower E. M. F., 
these secondary or transformer currents being 
utilized in the lamp circuits. 

By reason of the high pressure or electro-motive 
force employed in the primary or dynamo circuit 
the necessary electrical energy may be conveyed 
to the points at which it is to be used for the lamps 
over very small wires as compared with those re- 
quired for the Direct or Low Tension Systems, so 
called, which have heretofore been exclusively used 
for incandescent lighting. 

Reaching a point at which lights are to be sup- 
plied, the high pressure current is passed through 
a Transformer or Converter. 

The Transformer consists in effect of two coils, 
one of fine, the other of coarse wire, both wound 
on the same core of soft iron plates. See illus- 
tration on page 63. 

The high pressure current coming from the 
dynamo traverses the fine wire coil (called the 
"primar)^' coil) of the Transformer, and though not 



RECENT APPLICATIONS. 



63 



in contact or connection with the coarse wire coil 
(called the "secondary") produces in the second 
ary, by the electrical effect known as induction, 
an electric current differing, however, from the 
current in the primary coil, in that it is of low 
potential or pressure and suitable for use in the 
incandescent lamps. 




THE THOMSON-HOUSTON TRANSFORMER. 

From the Transformer lead the circuit wires to 
the building to be lighted, and the lamps are con- 
nected in the customary multiple arc or parallel 
precisely as in the Direct System, taking the trans- 
former as a source of supply instead of the dy- 
namo. 



64 



ELECTRICITY AND ITS 




RECENT APPLICATIONS. 65 

The Thomson-Houston Alternating Current Dyna- 
mo shown in the illustration differs very materially 
from the well-known type of machines made by 
this company, but has the same characteristics of 
excellence and embodies new and original ideas in 
dynamo design. 

The Thomson-Houston Electric Company recog- 
nizing the advantages of automatic regulation have 
produced a machine that, differing from any other 
on the market, is absolutely self -regulating for all 
changes of load, keeping the lights at a constant 
brilliancy. This is accomplished by an arrange- 
ment of the coils on the field magnets of the dyna- 
mo, called a "composite field/' 

A part of the magnetic field is maintained by 
means of current from a separate or exciting dyna- 
mo. If the load upon the outside circuit is in- 
creased, it is necessary to increase the magnetism 
of the field in order that the machine may in turn 
supply the increased demand in the circuit and the 
lights remain steady. 

This is accomplished in other machines by vary- 
ing the current on the field magnets by a rheostat 
or variable resistance operated by hand. In the 
Thomson-Houston Dynamo, however, the same re- 
sult is obtained entirely automatically by passing 
the greater portion of the main current through two 
or more of the field magnets, thus energizing the 
machine in exact accordance with the demands 



66 ELECTKICITY AND ITS 

made upon it. As an alternating current is not 
suitable for magnetizing the fields, it is necessary 
to change the character of the current produced in 
the armature to a direct current before passing it 
through the special winding on the field; and this 
is done by a commutator at the end of the shaft. 
By this regulation the attention required at the 
dynamo is reduced to a minimum, while at the same 
time the efficiency of the machine is increased, and 
any number of lamps from one to the full capacity 
may be thrown on or off without in any way affect- 
ing the steadiness and brilliancy of those remain- 
ing. 

To allow for a pre-determined percentage of loss 
in the wiring, it is necessary, as the load is in- 
creased, that there should be a definite amount of 
increase in potential, which is accomplished by 
placing around the field winding for the main cur- 
rent, a resistance which shunts that portion of cur- 
rent not required for regulation. 

The coils for Field Magnets are wound on spools 
which are slipped over the castings and fastened 
firmly in position. These being well protected, 
the liability of mechanical injury is reduced to a 
minimum. In case it is necessary to replace a coil 
or to remove the armature, the upper half of the 
field casting can be readily removed, leaving the 
parts easily accessible. 

The potential of the alternating current requires 



RECENT APPLICATIONS. 67 

that the utmost care be used in design and construc- 
tion of the armature. It is wound with one layer 
of wire, ample provision being made for insulation 
between the wire and the iron core, as well as be- 
tween the separate coils of which this layer is com- 
posed. These coils are carefully covered by a 
material possessing high insulating and protective 
qualities, and the whole is held in place by bands 
very firmly wound and fastened. The form of the 
core is such that perfect ventilation is secured, 
thereby entirely obviating any tendency to over- 
heating. 

The Collectors consist of two copper rings from 
which the current is conducted by means of narrow 
brushes, which require no adjustment, beyond that 
of the tension springs governing the pressure of 
the brush on the collector ring. 

The dynamo is supplied with a cast-iron base, 
or bed-plate which is provided with a ratchet belt 
tightener. 

For the purpose of energizing the field magnets 
the dynamos are furnished with small Exciting 
Dynamos of the direct current type. It has been 
found desirable in some special cases to make the 
smaller sizes of Alternating Current Dynamos self- 
exciting, and to this end the armatures are wound 
with an extra or special coil for furnishing current 
to energize the fields. 



68 ELECTRICITY AND ITS 

The Exciter is usually placed as shown in the 
cut, behind the alternating dynamo, driven by a 
belt from a small pulley attached to the armature 
shaft. One Exciter is usually employed with each 
Alternating Current Dynamo, but when several 
dyamos are operated in the same station it is often 
found more convenient to employ Exciters, any 
one of which is of sufficient capacity for all the 
machines. By this arrangement an accident to one 
Exciter need not affect the general service. 

As previously stated, when lights are required to 
be supplied at different degrees of voltage or pres- 
sure it is necessary to use what is called a trans- 
former, which is made on the principle of the in- 
duction coil. Having two coils, a Primary and a 
Secondary, and is operated by induction. By in- 
duction, we mean : "A current is said to be induced 
in a conductor when it is caused by the conductor 
cutting lines of magnetic force. A fluctuating 
current in a conductor will tend to induce a fluctu- 
ating current in another running parallel to it. A 
static charge of electricity is induced in neighbor- 
ing bodies by the presence of an electrified body. 
A magnet ' induces' magnetism in neighboring 
bodies." 

By sending the current from the dynamo through 
the smaller or primary wire the voltage is lowered 
in the secondary coil with a corresponding increase 
of quantity, or by sending the current through the 



JRECENT APPLICATIONS. 



69 




Figure 4. 



70 ELECTRICITY AND ITS 

larger or secondary coil ; the current in the pri- 
mary coil is raised in voltage, but is less in quan- 
tity. 

The two coils are carefully insulated from each 
other and from the iron core, thus preventing the 
high potential current from reaching the secondary 
or house line. As an additional security, in case 
any such connection is made, there is included in 
the secondary wiring of each transformer a Thom- 
son Automatic Protective Device which, in case of 
contact between the primary and secondary coils, 
will cut the transformer out of circuit. 

Transformers are made which may be used in 
connection with lamps of either 52 or 104 volts, it 
being necessary only to change a connection in the 
transformer for a change in the potential of the 
secondary circuit. A weather-proof iron case con- 
tains the transformer, with the necessary safety 
fuses and connections for the primary and sec- 
ondary wires. A special arrangement makes it 
possible to cut the transformer out of circuit while 
replacing fuses. 

The Station Transformer is used for supplying 
current for the potential indicator and lamps upon 
the switch-board. 

A diagram of a composite-field dynamo and con- 



nections is given in Fig. 4. 



KECENT APPLICATIONS. 



71 



The Westinghouse Alternating Current Dynamo 
for generating the alternating current is repre- 
sented by the accompanying illustration. 

The field is composed of a series of radial pole 
pieces having alternate polarity, the cores of which 
are cast solid with the base and cap respectively. 
The field coils are a series of bobbins, each inde- 
pendent of all the others, which are wound on 
shells, slipped over the pole pieces, and held up 
by bolts at the periphery, and these bobbins are 
supplied with a feeble current from the exciter. 




THE WESTINGHOUSE ALTERNATING CURRENT DYNAMO. 



The body of the armature is of laminated iron 
plates freely perforated for ventilating purposes. 
A single layer of wire is wound in flat coils back 
and forth across the face of the armature, in a di- 



72 ELECTKICITY AXD ITS 

rection parallel to the shaft, being retained by stops 
on the ends of the armature. Mica and other ade- 
quate insulation is provided, and the whole is 
wrapped with binding wire. A ventilator is attached 
to each end of the armature and draws a strong 
current of air through it. 

The total weight of copper on a 750-light arma- 
ture is 16 lbs., disposed in a single layer, which 
being on the surface is readily kept cool, and which 
can be inspected for deterioration or flaws of any 
character. A direct current armature of type most 
generally in use of 750 lights capacity, on the other 
hand carries more than ten times this amount of 
wire. 

The Brush New Alternating Current Dynamo. — 
The underlying principle of the Coreless Dy- 
namo here illustrated, was discovered and applied 
by Mr. Brush. 

In this machine the field magnets revolve, while 
the armature remains stationary. 

A brief examination shows that it is of the alter- 
nating type ; that its field magnets are many and 
carried by the shaft ; that the armature is fixed and 
absolutely free from any magnetic material ; that 
its parts are easily accessible, and that an armature 
coil may be cut out, removed or replaced without 
stopping the machine. 

The machine chosen for illustration and descrip- 



RECENT APPLICATIONS. 73 

tion has an output of 60,000 watts ; it supplies cur- 
rent for a thousand 16-candle power lamps. 

The shaft bearings, bearing standards, base plate 
and armature slides are cast in one solid piece. 
The centre line of the shaft is 16 and 11-16 
inches above the surface of the base plate, high 
enough for access to all parts of the dynamo, and 
low enough for steadiness and freedom from strain 



THE BRUSH ALTERNATING CURRENT DYNAMO. 

on foundations. The 4-inch steel shaft (tapering 
to three and a half inches in the bearings) carries 
two heavy cast-iron yoke pieces, 27 inches in diam- 
eter. To each of these are screwed, at equal radial 
and circumferential distances, the wrought-iron 
cores of 12 magnets of alternating polarity. The 
two yoke pieces, with their bolts, washers, etc., 
weigh about 950 pounds ; the magnet cores, 308 ; 
the magnet wire, 400. Thus the whole rotating 



74 ELECTEICITY AND ITS 

mass of cast-iron, wrought-iron and copper, acts as 
a fly-wheel weighing more than 1 700 pounds, and 
tending to neutralize any variation in the speed of 
the prime generator. As the nominal speed of the 
machine is fewer than 1 100 revolutions per minute, 
the structural strength is more than sufficient to 
meet all demands made by centrifugal force. Fur- 
ther than this, the mechanical stress is less when 
the magnets are excited than when the alternator 
is running without load, as the lines of magnetic 
force between the faces of opposing poles, tend to 
counteract centrifugal force. 

But the most interesting part of the alternator 
is the fixed armature shown in the full page engrav- 
ing. The vertical disc is occupied by flat armature 
coils, made of insulated copper ribbon wound on 
porcelain cores. The copper ribbon of each coil 
is reinforced on either side with strong insulating 
material of the same thickness as the porcelain. 
One of these reinforcements is grooved, and the 
other tongued. The coil, consisting thus of core, 
ribbon, and reinforcements, has an angular width of 
60 degrees. The upper part of each face of each 
coil is covered with an insulating plate, 5-16 of 
an inch thick. The coil thus built up and insula- 
ted is set in German silver holders, cut from true 
turned rings and held together by sunk-headed 
screws, as shown in engraving. Each terminal of 



RECENT APPLICATIONS. 




75 



ARMATURE OF THE BRUSH ALTERNATING CURRENT DYNAMO. 



76 ELECTRICITY AND ITS 

the copper ribbon connects with a binding post as 
shown. 

The six armature coils thus mounted are carried 
in a German silver frame consisting of two semi- 
circles bolted together on the line of the vertical 
diameter. The cross-section of this ring frame is 
girder-like. Into the slots of the frame-slip the 
six-mounted armature coils, the tongue on the edge 
of the one engaging with the groove on the edge 
of the next. The coils thus thrust into the intense 
magnetic field constitute a disc, 9-16 of an inch 
in thickness, and with an opening in the centre, 
through which passes the revolving shaft. As 
there is no magnetic metal in the armature, there 
are no local currents to waste the energy. 

The several coils are insulated carefully, and the 
stationary armature, as a whole, is insulated from 
the bed-plate on which it rests. The coils are joined 
in series, the binding-posts adjacent to any radial 
line of division between the two coils constituting 
fixed terminals for the main line. There is no com- 
mutator ; there are no collecting brushes to take 
the alternating current from rotating parts. 

The resistance of the armature coils is so low 
that it would seem impossible for one of them to 
burn out. But if one should, it may be removed and 
a new one readily put in its place in three minutes, 
or the injured coil may be shunted out of the cir- 
cuit and the dynamo kept running with the other 



RECENT APPLICATIONS. 7*1 

five until the time for shutting down. The coil 
section, complete, weighs about 20 pounds. 

In action, the 24-field magnets of the alternator 
are excited by the direct current from an 11 -inch 
Brush dynamo of the well-known form. This exci- 
ting current is carried to the brushes that rest upon 
the two uncut insulating rings, and thence through 
the hollow shaft to the magnets. A rehostat worked 
by hand or automatically is placed in the shunt-cir- 
cuit around the field magnets of the exciter, so 
that perfect regulation is secured without readjust- 
ment of the brushes or any necessity of handling 
the high-tension alternating circuit. 

The Brush- Pfannkuche "coreless" alternator is 
built at present for an E. M. F. of 2000 volts. 

On the following pages are given complete 
directions for making a small dynamo and motor 
for experimental and laboratory use. A machine 
that is not a toy, but capable of affording continual 
interest and profitable research, would be prized by 
any one of mechanical inclination. 

So many and curious are the applications of 
electricity that to realize their utility and signifi- 
cance, even faintly, is possible only by personal 
experiment and repetition. A set of chemical 
batteries can be called upon to supply a current of 
electricity, but such paraphernalia is inconvenient 
and expensive. Besides, the modern, and only 



78 



ELECTKIC1TY AND ITS 



practical method of generating the current is by 
dynamos. 




Figure 5. 




Figure 6. 



Motors, much like dynamos in construction, run 
our work-shops and railways. The young candi- 
date for electrical qualifications may consider that 



KECE.NT APPEliJATlO^S?. 79 

he has passed excellent preliminary examinations 
if he constructs and owns a practical dynamo. 

Figures 5 and 6 in this article show a dynamo 
(or motor) of simplest design, but a marvel of 
adaptability. The frame, comprising the field 
magnets and supports for the armature bearings, 
is in but two pieces. The armature is made of one 
piece of iron, with one coil of wire. Yet this small- 
machine will require one-man power to drive to its 
full capacity, and will make a very energetic motor. 
It will generate a current, whether turned in one 
direction or the other. As a motor it can be made 
to run at will in either direction. Furthermore, it 
is capable of doing what seems impossible — it 
can furnish a current in a continuous or alternating 
direction. No laboratory or electrical cabinet is 
complete without some means of getting an 
alternating current. For a continuous current the 
brushes rest on the commutator, as shown in the 
cut. In this case it is self-exciting; that is, the 
dynamo is complete in itself and magnetizes its 
own fields. By running one brush on each of the 
rings, shown on each side of the commutator, and 
" separately exciting" the fields from some other 
source, an alternating current is available. By 
another arrangement of internal connections the 
commutator and collector can be capable of making 
a " self-exciting, alternating current dynamo/' 



SO 



ELECT1UC1TY A.ND ITS 




RECENT APPLICATIONS. 



81 




82 ELECTKIC1TY AND ITS 

Such a combination is not attempted by any 
machine novv on the market. 

By winding proper sizes of wire on the armature 
and field cores, any strength, or "potential/' of 
current can be obtained. For ordinary uses a cur- 
rent of 25 volts will be found convenient. No. 18 
wire on the armature, and No. 14 on the fields 
would do this. 

At this potential eight amperes could be secured. 
A higher potential, but less current would result 
from use of fine wire, or a lower potential and more 
current with larger wire. 

The working drawings with dimensions show the 
construction so clearly that a detailed description 
is almost superfluous. Making the patterns is tedi- 
ous, and perhaps inconvenient, and with foundries 
distant, it may be impossible for each one working 
independently to avail himself of this article. By 
clubbing together, only one set of patterns would 
be needed, and castings obtained at low rates. 

The upper and lower parts a and b of the frame, 
the caps for the bearings and the pulley are of 
common cast-iron ; the armature of annealed cast- 
iron. The rest of the metal parts, except the shaft, 
are of brass. 

In making this machine, the four legs are first 
to be filed or planed flat, to secure a firm rest on 
the planer. For the next step, plane the parts where 
the halves of the fields bolt together, and where caps 



KKCENT APPLICATIONS. 



33 





84 



ELECTKICITY AND ITS 



screw on. The holes may then be drilled, tapped, 
and screws inserted. After the caps c and d are 
tightly screwed in place, the builder may proceed 
to bore out the f-inch holes where the bearings of 
the armature shaft are to rest This can best be 




done with a boring bar in a lathe. Or these may 
be drilled between lathe centres, if the holes are 
afterwards reamed together to insure exactness. 
The outside and inside rims should be faced smooth 
that the linings may fit nicely, 



BECEA'T APPLICATIONS. 



85 



To bore out the fields is usually troublesome ; 
but in this machine the boring is easily accom- 
plished. After the arms are finished, as first di- 
rected, a boring bar f-inch in diameter, with a cut- 
ter head in the centre can be laid in place, using 
the arms as supports. The boring to size can then 
be done in any screw cutting lathe. 




Hard brass or gun metal is suitable for the bear- 
ings or lining e and f. These are to be made in 
one piece each, instead of in halves. They are 
thus easily made, and cheaply replaced when worn 
out. The oil cups g enter the small hole in the 
top and prevent the linings from turning 



8fi 



ELECTKICITY AND ITS 




KJbXENT APPLICATIONS. 81 

The armature casting h should be annealed by 
heating to a bright red, and then cooled slowly ior 
several hours. Drill the /s-inch hole through che 
centre and dri^e it upon a short arbor ror turning. 
The outside diameter is to be just 2 inches. As 
the field bore is 2 1 1 6 -inch, there will be, when the 
armature is in place, ^-inch clearance. Turn the 
shaft i to its specified dimensions and drive the 
armature tightly on the centre portion ; a few i-inch 
steel pins will insure non-loosening. The pulley k 
is to be fitted to the 5-16-inch end of the shaft and 
held in place by two set-screws butting on flat- 
tened spots. 

As it is difficult to work copper, brass can be 
used for the commutator and collector. Boxwood 
or hard rubber will make a good hub. The com- 
mutator or centre portions m should be first made. 
Fit the tube tightly to the centre, and put in the 
small screws ; then remove the tube and saw it in 
halves. Groove the wood for the connecting wires 
^nd fit on the two collector rings n. Again remove 
the brass tubes and solder the connecting wires in 
place. One wire is to connect with the inside ring 
and one commutator segment ; the other wire with 
the outside ring and opposite segment. A small 
pin should be put in the shaft to keep the commu- 
tator from slipping. Make the position of the 
division between the commutator segments as 
shown in the figure. 



88 



ELECTK1CITY AiSJJ IT6 



Fit the yoke o to the inside rim of the short lin- 
ing and tap the hole for the set-screw/. Studs or 
spindles q for the brush holders, enter the ends of 




"* 



* 



® 







r 

1 






J 

1 



(P ^ 



the yoke suitably insulated with hard rubber wash- 
ers and bushings r and s. Three pieces only are 
used to form the brush holder, — an outside part /, 



RECENT APPLICATIONS. 



bv 




and inside part tc, and the screw v. When the screw 
is tightened the brush w (of leaf copper), and stud 
g is tightly clamped. The brass ears x into which 
the flexible cables are soldered, are opened to the 
centre hole to allow easy removal. 



90 



ELECTRICITY AND ITS 



i 



I 









-2'A 



<JL 



'C 



fb 




/*-*.+ 



Tap. 



A maple connection board y surmounts the ma- 
chine. One screw in the centre is sufficient to 
hold it. The brush holder cables end at two of the 
binding posts, the field wires at the other two. 

The builder is now ready to wind on the wire. 
File off any roughness on the iron, and insulate 
with several layers of manilla paper well shellaced. 
The armature is to be wound like a shuttle until 
filled, with No. 18 double cotton covered magnet 
wire ; about I- \ pounds will be required. The four 
sections of the field will take, in all, eight pcands 
of No. 14 wire. Each section is to be wound in 
the opposite direction from its neighbors, in order 
to make consequent poles around the armature. 

Fig. 7 represents a diagram of the winding. 



BECENT APPLICATIONS, 



Wl 



Gf§| 



m 





iS 



hid «* fPy-tl 



.3 



6 



J. 







HH 


© 




VH'l 


a-J^^p 


l EST 






re 





92 



ELECTRICITY AND ITS 




d-3*TKJU 



* 



Shttt copper 

VY 



T 
1 




L4M£2 



f*r> /Q-A.+ A*m,«\. s-crc,*- 



SECEXT APPLICATIONS. 



93 




Figure 7. 
When used as an ordinary series machine the line 
wires enter 1 and 3, or 2 and 4, the other two being 
connected with a short wire. The diameter in 
which the dynamo runs is determined by these con- 
nections. The same holds true when used as a 
motor. If an alternating current is desired, the 
line is supplied from 1 and 2, while a separate cur- 
rent must be supplied to 3 and 4 to magnetize the 
fields. Only two brushes are to be used, one on 
each collector ring. 

In case a self-exciting alternating current dyna- 
mo is built a specially connected commutator-col 
.ector and yoke are used. 

Fig. 8 clearly shows the connections. Six brushes 
are necessary. The alternating current generated 
in the armature first passes to one of the commiv 



94 



.ELECTRICITY AND ITS 



tfctrper wtre 



Solder 




Solder 



COMMUTATOR FOR SELF-EXCITING ALTERNATOR. 

tator segments, then from one set of brushes, in a 
continuous direction through the field winding back 
to the other set of brushes. By contact of these 
brushes alternately with one segment, then the 
other, the current is directed alternately again into 
the outside collector ring, through the line wire, 
back to the other ring, and the circuit is completed. 

Other forms of armatures can be designed for 
use in these fields, a drum, or even a ring arma- 
ture with many segments in the commutator. The 
field winding may be made shunt, especially for 
running incandescent lamps. Even a compound 
field is possible. 

For continued use, this dynamo would be driven 
from a line of shafting ; but for experiments of a 
few minims' duration hand or foot power is a A *n is- 
sabie. 



EECKVI' APPLICATIONS. 



95 




Figure 8. 

Fig. 9 represents a simple contrivance for driv- 
ing by hand. A cast-iron frame, light but well 
ribbed, is secured to a board or table a few feet 
from the dynamo by two thumb screws. A wheel 
15 inches in diameter, 1 ^-inch face, driven by a 




A 



3g £^P 



t3 



Figure 9. 



U 



96 



ELECTRICITY AND ITS 





yoke for Self E*citL*tf dUernater _ % 
JYos.la^atl are for CQTrL7***-u.tator brushes 

handle on one of the spokes will get up sufficient 
speed to run two 16-candle power incandescen" 
lamps, or to run a small arc lamp. 

Various means have been devised for transmit- 
ting power from the steam engine to the dynamo, 
as using different kinds of belts, or connecting the 
shaft of the dynamo directly with tne shaft of the 
engine, the object of each method being to ob- 
tain a certain result. Belts are used for ordinary 
purposes, as in centra! stations, private plants, etc. 

In electric lighting on steamships the dynamo is 
usually connected with the shaft of the engine, as 



RECENT APPLICATIONS. 



97 



the motion of the boat would interfere with driving 
of the dynamo by loosening the belt. 

An illustration of this is given below of the 
American Engine Company's system. 




AMERICAN ENGINE COMPANY'S DIRECT CONNECTED 
DYNAMO AND ENGINE. 



ELECTRICITY AND ITS 



CHAPTER IV. 

THE ELECTRIC ARC AND THE ARC LAMP. 

In 1810 Sir Humphrey Davy discovered the 
phenomena of the electric arc. His description is 
as follows : 

"When pieces of charcoal about an inch long 
and one-sixth of an inch in diameter were brought 
near each other (within the thirtieth or fortieth 
part of an inch) a bright spark was produced, and 
more than half the volume of the charcoal became 
ignited to whiteness ; and by withdrawing the 
points from each other, a constant discharge took 
place through the heated air in a space equal at 
least to four inches, producing a most brilliant 
ascendant arc of light, broad and conical in form 
in the middle." 

Of course the light did not last long, as the 
charcoal, being soft, burned rapidly away. 

The necessary current was supplied by a battery 
of 2000 cells, with zinc and copper plates, the 
exciting fluid being dilute sulphuric and nitric 
acids. 

Davy touched the charcoal points together 



RECENT APPLICATIONS* 99 

horizontally after attaching the wires to the bat- 
tery, and then separated them. The stream of hot 
flames which followed or joined the points were 
deflected by air currents and took the form of an 
arch or curve, which gave the name to the phe- 
nomena. 

There have been a great many ideas given in 
regard to the nature of the electric arc. Prof. 
Thomson says in his excellent paper, read before 
the recent convention of the National Electric 
Light Association, held at Providence, R. I.: 

"Let an attempt be made to separate any part of 
a circuit in which the current is maintained by a 
sufficient e. m. f. or potential, and we find that if 
the separated ends are moved quickly we get a 
flash or spark of varying length, which becomes a 
flame of great heating effect if the current be of 
high rate of flow. If the separation of the two 
parts of the circuit be made slowly a continuous 
flame or discharge will take place between the 
ends if they be not too widely separated or so 
widely separated that the potential or pressure of 
the current is not sufficient to force current across 
the space. With considerable potentials and heavy 
currents a space of many inches may thus be 
bridged. Whether the separated ends be of iron, 
copper, carbon, platinum, zinc or other conductor, 
the hot discharge is still formed. Therefore, while 
the electric arc is generally spoken of as that flux 

LofC. 



100 



ELECTEICITY AND ITS 



occurring between carbon ends separated, of course 
it cannot be so limited, and we frequently, there- 
fore, refer to copper arcs, iron arcs, carbon arcs, to 




THE ELECTRIC ARC CARBONS. 

distinguish one from the other. What, then, is the 
arc so formed ? Is it heated air between the ends 
separated, containing detached particles of the 



RECENT APPLICATIONS. 101 

conductor in process of carriage, as was apparently 
thought for a long time to be the case ? No, the 
arc proper is composed of a stream of vapor arising 
from the actual boiling or vaporization of the solid 
or fused ends of the separated conductors. In so 
far as the surrounding air mixes or combines with 
this vapor stream, it is modified by the presence of 
oxygen and nitrogen, but the air or any other gas 
is not essential to be present, and is merely inci- 
dental to the formation of the true arc stream in 
air. Indeed, it may seem strange to some to speak 
of vapor of carbon, copper, iron, platinum, etc., but 
their production is merely a question of tempera- 
ture in any case. In the electric arc there is a 
real distillation of the conductors forming it, and 
this accounts for the variation of color and temper- 
ature to be found in different arcs. The copper 
arc evolves a peculiar green light, which is 
exceedingly trying to the eyes, as those who have 
experienced its effects well know. Zinc gives a 
whiteish blue, while the carbon arc proper is 
purplish in tint. The arcs from various metals 
give in the spectroscope the characteristic lines of 
the vapor of each metal. 

As a curious incident, showing the presence of 
the metal vapor in the arc, I may mention the fact 
that when by accident a person has had a portion 
of his clothing bathed for an instant in a heavy 
copper arc caused by a short circuit of heavy cur- 



102 ELECTRICITY AND ITS 

rent mains, there has been found a considerable 
deposit of copper ; enough, in some cases, to give 
the reddish color of copper to the surface bathed, 
which, if moistened, turns green by oxidation. It 
also gives a deep blue to dilute ammonia in which 
it is washed, thus showing the presence of copper. 
In like manner these metallic arcs will give a 
deposit of the metal on cold surfaces which they 
touch. 

It appears to be the positive pole which gives 
out the vapor stream. With carbon the positive 
vaporizes steadily and is consumed much faster 
than the negative. In the use of the arc, however, 
for lighting, we have learned to distinguish what 
is called "a short arc" and a "long arc" system. 
In "short arc" systems the carbons are burned 
much nearer together than in the " long arc " 
systems. Let us suppose the case of two carbons 
touching each other with a current passing, and 
then that we very slowly separate them, stopping 
to observe effects. When the contact is light 
before actual separation, a visible heating of the 
meeting ends is seen. On attaining a small 
separation the space between seems filled with hot 
vapor and we have a short arc, where the separa- 
tion is perhaps not over two or three one-hun- 
dredths of an inch. There is also noticed an 
active transfer of carbon from the flattened end of 
the positive, and a deposition of carbon on the end 



RECENT APPLICATIONS. 103 

of the negative carbon. This deposited carbou 
takes the form of a mushroom, and, after a time, 
breaks off. Meanwhile combustion goes on at 
both poles and wears away the sides of the positive 
carbon, while the transfer of carbon wears away its 
tip or crater. The burning also wears away the 
negative at the sides, while the tip is built up by 
the mushroom deposit from the arc. But the 
cutting in of the negative finally severs the mush- 
room tip and it falls away. Hence both carbons 
are eventually consumed. To develop a short arc 
there is required a little over half the potential 
that is needed for a "long arc," or about 25 volts, 
more or less, and therefore to give out equal heat 
energy in the arc the current must be double in 
the short arc over what it would be in the long arc. 
The short arc is subject to the objection of a con- 
tinual frying sound emitted, and great variations of 
luminosity ; it requires a very dense and hard 
carbon to conduct the current without great loss, 
and involves line loss of at least four times the 
amount with the long arc if equal gauge wires be 
used. 

In fact, while in the past such arcs were com- 
mon, their number is diminishing, as they are 
being replaced by the more efficient and completely 
developed arcs called "long arcs," which are so 
called to distinghish them from the "short arcs." 
Returning to our separating carbons we find that 



104 ELECTRICITY AND ITS 

as the space or arc is lengthened from the short 
arc condition we pass a stage of great flickering 
and unsteadiness, and a fluctuating potential 
between the carbons, and then reach the stage of 
the long or quiet arc. With ten amperes the 
separation may now be about 1-16 to 1-10 inch or 
more. Smaller currents require less separation 
and larger ones an increased separation. At this 
stage the arc is quiet, with good, pure carbons 
very steady, and the potential difference remains 
at about 45 volts, if, of course, the carbon is 
properly fed to make up for combustion. The 
perfect arc is really a beautiful phenomenon. 
While the positive carbon still loses by volatiliza- 
tion from its tip or crater, and by combustion from 
its sides, the negative gains no deposit, but wastes 
at a less rate than the other, and by combustion 
only. The carbon vapor carried off from the 
positive is consumed by the oxygen of the air 
before it can deposit on the negative. Hence the 
outer zone of flame, which can easily be distin- 
guished from the central zone or arc flux proper, is 
probably a zone of combustion similar to that 
existing in ordinary flames. The removal of 
carbon by vaporization from the positive end gives 
rise to the crater or cup, which is so prominent a 
feature of carbon arcs produced by continuous 
currents. The size or area of the crater is a rough 
measure of current strength, but varies with 



RECENT APPLICATIONS. 105 

different qualities of carbon. With very long arcs 
the crater or hollowed end disappears and the ends 
become rounded. A well-formed crater with the 
arc of flame confined thereto means usually a 
steady light, since the chief source of light in an 
electric arc is from the positive crater, which shines 
like a diminutive sun and represents the hottest 
part of the arc. The vapor light proper, or flame 
light, is comparatively very feeble and of a purple 
quality in air. Hence the arc light is as truly an 
incandescent source of light as is the incandescent 
carbon filament, with the difference that to run the 
latter at the temperature of vaporization or boiling 
point of carbon, so to speak, means instant 
destruction, while by the necessities of the case 
the light obtained from the arc is chiefly that 
emitted from a surface of carbon at its temperature 
of boiling, or more correctly of sublimation at 
atmospheric pressure. This temperature is ex- 
ceedingly high, and accounts for the well-known 
superior economy in light production of the arc 
over all other kinds of lighting. 

The temperature of the positive carbon crater is 
so high that the carbon exists there in a soft or 
plastic condition, capable of receiving an impression 
like putty. I have proved this with very large 
arcs of 1 50 to 200 amperes, by suddenly forcing 
the carbons together when the current had been 
cut off, and finding that they would fit each other 



106 ELECTRICITY AND ITS 

perfectly, the negative impressing its form on the 
positive crater/' 

Thus you see that the electric arc is simply, the 
heated vapor in the space between two electrodes, 
produced by a current of electricity leaping across 
it. 

A great many interesting experiments have been 
made with the electric arc and perhaps our readers 
would be interested in the following article, 
entitled " An Experiment with the Electric Arc," 
by Wm. Stanley, Jr., which was published in a 
recent numberof the Electrical World : 

" Prof. Thomson's paper on arc lights calls to 
my mind an experiment in the laboratory some 
time ago with an alternate current arc, which pre- 
sented a very beautiful illustration of the deflecting 
power of a strong magnetic field. Inside a hollow 
carbon tube about two inches in diameter was 
placed an ordinary seven-eighths inch carbon, 
separated from the tube by about one-quarter of 
an inch air space all around, except where it was 
held in place by an insulating ring, as shown in 
Fig. i. A coil of wire connected in series with 
th.e carbons, and with a constant current trans- 
former by a flexible cord, was mounted to a handle 
for convenient handling. 

If an arc was started between the inner carbon 
and the concentric tube, and if the coil was 
approached parallel to the face of the carbons, the 



RECENT APPLICATIONS. 



107 



arc revolved around the centre carbon after the 
manner of a pin-wheel. Reversing the face of the 
coil — that is, the direction of the field threading 




FIG. 



■ROTATION OF THE ELECTRIC ARC. 



the arc— -caused an instantaneous reversal in the 
direction of rotation of the arc. 



108 



ELECTBICITY AND ITS 



When the coil was placed around the concentric 
carbons and near the arc, the latter became dis- 
torted, as shown in Fig. 2, while it continued to 
revolve about the axis of the coil. 




FIG. 2. — SIMULTANEOUS REPULSION AND ROTATION 
OF THE ARC. 

Many modifications will suggest themselves to 
any one attempting the experiments. One point 
observed by Prof. Thomson was very clearly 
evidenced, which was that when the arc was 



RECENT APPLICATIONS. 109 

whirling (and it might be made to whirl so rapidly 
as to appear continuous about the centre carbon) 
the potential required to maintain a constant cur- 
rent rose enormously ; so high, in fact, that the 
transformer was often unable to supply the demand 
for increased potential necessary to maintain the 
arc, although it was constructed to deliver a con- 
stant current from short circuit to 800 volts ; as a 
consequence, the whirling arc would repeatedly 
blow itself out with a loud report if the deflecting 
coil was approached very near the seat of the arc. 
Of course, the arc revolves and becomes distorted 
because of the reactions between the field produced 
by the coil and the weaker field about the arc, and 
an apparent continuous effort exists between the 
two fields to coincide or join together. Many 
beautiful lecture and demonstration experiments 
for classes may be obtained from this same simple 
apparatus, which, of course, may be operated with 
equal success by either alternate or direct cur- 
rents. 

The Arc Lamp now in general use consists sim- 
ply of two hard carbon rods, one above the other, 
and a mechanical contrivance to feed them. 

It is necessary that the mechanism should start 
the arc by ceasing the pencils to touch and then 
separate them to the requisite distance for the 
production of a steady arc ; it should also cause the 



.210 ELECTRICITY AND ITS 

carbons to be fed into the arc as fast as they con- 
sume, and to approach or recede automatically, in 
case the arc becomes too long or too short ; it 
should further bring the carbons together for an 
instant, to start the arc again if it should go out. 

There are a great many forms of arc lamps, but 
the one in general use by a number of the large 
companies is the clutch lamp. This is a simple 
device, consisting of a clutch to pick up the upper 
carbon holder, the lower carbon remaining fixed. 
The clutch is worked by an electro-magnet, through 
which the current passes. If the lamp goes out 
the magnet releases the clutch, and the upper 
carbon falls by its own weight and touches the 
lower carbon. Instantly the current starts round 
the electro-magnet, causing it to act on the clutch, 
which grips the carbon-holder and raises it to the 
requisite distance. When the arc grows too long 
the lessening attraction on the clutch permits the 
carbon-holder to advance. 

Fig. 3 shows the Brush Electric Co.'s arc lamp. 
This is a double-carbon lamp and when one carbon 
has burned cut the current is shifted automatically 
to the other, thus making the life of the lamp twice 
as long. 

Fig. 4 shows the new short arc lamp of the 
Thomson-Houston Co. This lamp differs from 
the long lamp, by having quite a novel feeding 
apparatus. The upper carbon dutch is attached 



BECENT APPLICATIONS. 



Ill 





Figure % 



212 



ELECTKICITY AND ITS 




Figure 4. 

to a brass ribbon, which is wound around a wheel 
having a ratchet and pawl, operated by an armature 
and an electro-magnet. The ribbon is unwound 
in this manner, feeding the upper carbon into the 
arc as fast as needed. 

Arc lamps are usually operated in series, that is, 
the wiring is so arranged that the whole current 
starts from the dynamo and continues through the 
carbons of each lamp until it completes the circuit 
back to the dynamo. See Fig. 5. This requires 



RECENT APPLICATIONS 



113 



high voltage, each lamp requiring about 50 volts 
to operate it, therefore an ordinary dynamo with a 
capacity of 3000 volts will run about 60 lamps. 

In this way of wiring, should anything happen 
to one of the lamps to prevent the current passing 
through it, there would be no way for the current 
to go any further, consequently all the lamps 




Figure 5. 

would go out. To avoid this difficulty a shunt is 
employed around each lamp, which acts 'only when 
the lamp will not light. 

The Naval Projector is an apparatus consisting 
of a focusing lens and an arc lamp, mounted n. 
such a manner that a strong light of 6,00c tc 



m 



SLECTBICITY AND ITS 




THOMSON- HOUSTON NAVAL PROJECTOR ARC LAMP. 



BECENT APPLICATIONS. 



11. 




THOMSON-HOUSTON NAVAL PROJECTOR 



116 ELECTRICITY AND ITS 

10,000 candle-power can easily be thrown in any 
direction at rapid intervals. 

On page 115 will be found an illustration of the 
Thomson-Houston Naval Projector. 

They have been adopted by the Bureau of 
Ordnance of the United States Nav-v, and have 
been installed on the cruisers Yorktown, Baltimore, 
Philadelphia, Charlestown and Newark. Projectors 
have also been ordered for several additional 
vessels. . 

The lamp, see illustration on page 114, is fed by 
turning the adjusting screw near the base by hand, 
which brings the carbons to the requisite distance 
as needed. Search lamps, which are made smaller 
than the naval projectors, were recently used in 
the night, during the flood in the Mississippi 
Valley, in discovering and rescuing the unfortunate 
people from drowning who were floating about 
helplessly on raits, etc. 



RECENT APPLICATIONS. 117 



CHAPTER V. 

ELECTRIC MOTORS AND HOW TO BUILD ONE. 

Practically an electric motor is a dynamo re= 
versed, it being a machine furnishing power and is 
actuated by a current of electricity, generally 
furnished from a dynamo or an electric battery. 

The field winding of motors is adapted to the 
work which the motor is to perform. For constant 
speed the shunt winding is used. Compound 
winding is theoretically more correct, but a shunt 
winding will regulate the machine closely enough 
for all practical purposes, and is the one most 
commonly used. Series winding is used where a 
variable speed is required and where the regulation 
can be attended to by hand. Its chief advantage 
is in its great starting power. 

Recently the advantages of low speed motors is 
attracting the attention of electricians. To this 
class belongs the Perret motors. 

The Perret Motor. — The chief distinctive feature 
of this machine is the lamination of the 'field 
magnet. Instead of casting or forging this in 
several solid pieces, as is usually done, it is built 



118 ELECTRICITY AND ITS 

of thin plates of soft charcoal iron, which are 
stamped directly to their finished form and 
clamped together by bolts in such a manner as to 
secure great mechanical strength. 

The advantages of such a construction are, in 
brief, a magnetic field of great intensity and the 
entire prevention of all wasteful induced currents 
in magnets and pole-pieces. 

The armature core is also laminated, and the 
plates have teeth, which form longitudinal chan- 
nels on its periphery, in which the coils are wound. 

The plates in both field and armature are in the 
same plane, and are of soft charcoal iron, with 
its grain running in the direction of the line of 
magnetic force, and there is the least possible 
break in the continuity of the circuit, there being 
no air gap between the iron of the field and the 
iron teeth of armature, except that required for 
clearance in rotation. Thus we have a magnetic 
circuit of lowest possible resistance, and it follows 
from well-known laws that we secure the maximum 
of effective magnetism with a minimum expendi- 
ture of magnetizing power. 

The armature coils being practically imbedded 
in the armature, receive the highest inductive 
effect from the intensely magnetized iron. 

The high efficiency which such construction 
should give theoretically is practically demonstrated 



RECENT APPLICATIONS. 119 

by the machines in actual work, and ranges from 
yof) in the smaller to g$fc in the larger. 

Attempts have been made by many since the 
days of Pacinotti to use toothed armatures, but 
with the result that very troublesome and waste- 
ful heating effects were produced in the solid 
magnets and pole pieces commonly used. With 
laminated field magnets these disadvantages are 
avoided, and we are able to secure the advantages 
enumerated, as well as others, among which may 
be mentioned the important ones, positive driving 
of the armature coils and less liability of winding 
out of balance. 

It will be seen that the armature is a ring of 
comparatively large diameter, with longitudinal 
channels on its periphery, in which the conductors 
are wound, and thus embedded in the iron, which 
is in such close proximity to the iron pole pieces 
that there is practically no gap in the magnetic 
circuit. 

The field consists of three separate magnets 
arranged at equal distances around the armature, 
each magnet having two pole pieces. See Fig. I. 
The winding is such as to produce alternate North 
and South poles. The magnets are built up of 
plates of soft charcoal iron, which are shaped as 
shown in the diagram, and the magnet thus pro- 
duced is of such a form that it may be readily 
wound in a lathe. A non-magnetic bolt passes 



120 



ELECTKICITY AND ITS 



through a hole in each pole piece and the plates 
are clamped together between washers and nuts 
on the same. These bolts also serve to attach the 
magnets to the two iron end frames, which are of 
ring shape and are bolted to the bed plates of the 
machine, 




Figure i. 



The magnetic circuit is of unusually low resist- 
ance by reason of its shape, its shortness, which is 
shown by the diagram, and the superior quality of 
iron used. 



RECENT APPLICATIONS. 



121 



There is no magnetism whatever in the frame, 
bed or shaft of the machine, as the magnets are 
supported at some distance from the frame by 
means of the non-magnetic bolts, and the armature 
is mounted on the shaft by spiders of non-magnetic 
metal. 




THE PERRET MOTOR. 



There is therefore no opportunity for magnetic 
leakage, and, furthermore, the whole is enclosed by 



122 ' ELECTKICITY AND ITS 

a shield or case of sheet metal, as shown in the 
illustration on page 121. 

The practical advantages of low speed machines 
are many. For instance, in ordinary machine 
shops, wood-work shops, printing offices, etc., the 
shaft is commonly run 200 to 300 revolutions per 
minute, and it is a simple matter to belt direct to 
it from a motor running 500 to 600 revolutions, 
thus saving the first cost of a counter-shaft and one 
belt, and saving, also, considerable power which 
would be lost in transmitting through the counter- 
shaft and additional belt, which would be used 
necessarily with a motor of high speed. The 
advantage is equally as great in case of elevators 
operated by a belt from the motor, and indeed, it 
is possible to gear direct from the motor to the 
elevator. 

The United States Electric Motor shown on page 
123 is peculiarly adapted for small plants. The 
armature, as will be seen, is completely enclosed 
by the field frame and the gauge screen on top ; 
and in addition, the wires constituting the winding 
are all below the surface of the armature. It is 
claimed that this latter feature, besides contribu- 
ting to the safety of the machine, is of great 
advantage otherwise. The air space is much re- 
duced thereby, producing a machine of high 
efficiency. To prevent loss and heating in the 
pole pieces, due to eddy-currents induced by the 



RECENT APPLICATIONS. 



123 




THE UNITED STATES ELECTRIC MOTOR. 



124 ELERICTCITY AND ITS 

rotation of the armature, the faces of the pole 
pieces are built up of fine laminae, in a similar 
manner to the armature. 

The machines are compound-wound, so as to 
preserve a constant E. M. F. under varying loads, 
or to raise the E. M. F. by a given percentage, 
with increase of load, as may be desired. 

The C. & C. Electric Motoric illustrated on page 
125. The standard machines are shunt-wound, 
and resistance of fields and armature is so care- 
fully proportioned that the speed is practically 
constant under the greatest variations of load. 

The magnetic circuit is of the consequent pole 
type, which gives the compactness of design. 
It is made in the circular form, having divided or 
parallel circuits meeting at top and bottom and 
passing together through the armature core. It 
consists of two cores, shaped like segments, of a 
circle bolted to pole pieces at both ends, surround- 
ing the armature. The cores are of wrought-iron, 
planed off at the ends to an angle of ninety 
degrees, so that when the machine is put together 
each core and pole piece forms a quadrant of a 
circle, the centre of which coincides with the centre 
of the armature shaft, which is the only shape that 
makes it possible to attain a high magnetic 
efficiency. This construction gives a very short 
magnetic circuit, free from corners or projections 
where leakage may occur, and makes the motor 



RECENT APPLICATIONS. 



125 



exceedingly compact for a given power. The pole 
pieces are of cast-iron, of much greater cross 
section than the cores, the lower one being cast in 
one piece with the base. They are bored out by 
special machinery of great accuracy, and' the sur- 
faces to which the cores are bolted are planed with 
exactness. The bolts passing through the poles 
are of ample dimensions, having their heads sunk 
into the casting, so as not to make any projection 
from the smooth surface of the pole pieces. The 




THE C. & C. MOTOR. 



cross sectional area of pole pieces and armature 
core is always much greater than that of the field 
cores, and the clearance allowed between armature 
and poles is reduced to the lowest amount consis- 



126 ELECTKICITY AND ITS 

tent with safety, being never more than 3~64ths oi 
an inch. The poles enclose about 280 degrees of 
the armature circumference. 

The field magnet coils are wound directly on the 
cores by hand, and the greatest care is exercised 
in winding. By this method the coils are brought 
very close to the core, and the wire is under con- 
tinual inspection during the winding. Cotton 
covered wire of the best insulation is used, and an 
extra covering of oil paper is added wherever it is 
considered advisable. The coils, after being 
shellaced and dried in an oven, are measured to 
standard resistance and insulation before they are 
passed from the winding room. When finished 
they are covered with canvas and rubber tape 
painted with black varnish, which ensures perfect 
protection to the wire. 

The armature is built upon a steel shaft and the 
shaft is turned down and is of considerably greater 
diameter at its centre than at the ends running in 
the bearings. The armature core is a drum, made 
up of thin discs of sheet-iron, insulated carefully 
from each other. These are stamped with a hole 
in the centre for the shaft, and after placing them 
on the shaft they are compressed together with 
great force. Iron arbor plates, keyed to the shaft 
at the ends, hold the discs firmly in position, and 
are themselves held by nuts screwed on the shaft. 
These discs are in addition held together by long 



BECENT APPLICATIONS. 127 

bolts, whose heads are sunk into the arbor plates, 
thus ensuring an absolutely rigid and solid core. 
The finished core is turned smooth in a lathe and 
is then ready for winding. In winding, the core is 
first thoroughly insulated with mica and oil paper. 
A modification of the Siemens winding is employed 
and the wire is proportioned to carry an excess of 
current above the full load of the motor, without 
undue heating. In all cases where wires cross in 
winding the insulation is fortified with silk and oil 
paper. The motor is so designed as to allow the 
use of the wire on the armatures of much larger 
size than the rated capacity of the motors actually 
require, thus making it practically impossible for 
the armatures to burn out. They are bound by 
narrow bands of German silver wire placed to- 
gether and wound on mica strips. Canvas, painted 
with asphalt varnish, covers the armature heads and 
is secured to a fibre washer, fitting tightly over the 
shaft at one end, and to a groove in the commuta- 
tor at the other. 

The armatures are dried and tested for insulation 
before the canvas covers are put on. Double 
insulated wire is used on all armatures, and after 
completion, all armatures are balanced with the 
greatest care to insure noiseless running. 

The commutator is built up of cast tempered or 
of hard drawn copper bars of tapering cross section 
beveled at each end. The insulation between the 



128 ELECTRICITY AND ITS 

bars is of mica, made up of thin strips. They are 
held together by steel collars, turned on one side 
to the same angle as the ends of the bars and 
carried on a brass sleeve fitting on the shaft. The 
sleeve is threaded at both ends to receive nuts, 
which are screwed up against the collars, thus 
holding the bars firmly in place without allowing 
them to twist out of line. The sleeve and collars 
are carefully insulated from the bars by thick 
layers of mica. 

The base is of cast-iron, very rigid, of which the 
lower pole piece forms a part. Its length is con- 
siderably greater than its width, All the surfaces 
to which the field cores and pedestals are bolted 
are planed true and finished to a smooth polished 
surface, so as to prevent the slightest loss of 
magnetism from poor joints. The motor rests 
upon iron rails fastened to a wooden base frame, 
which allows of the adjusting of the machine to 
take up any slack in the belt. 

The pedestals are of cast-brass and are very 
short, heavy and of great strength. Brass is used 
to prevent any tendency to magnetic leakage. 
They are bolted to planed surfaces at the ends of 
the beds by four bolts, and are guided to their 
exact positions by two dowel pins. They are also 
provided with an oil well and pet cock for carrying 
off the oil drip. 



KECENT APPLICATIONS. 129 

The bearings of all motors are of a brass alloy, 
particularly well adapted to this purpose, and are 
in the form of a sleeve, having a convex bearing 
surface at the centre, which rests on a concave 
surface on the pedestal. The bearings are thus 
self-aligning, which prevents any danger of bind- 
ing. The inside of the bearing is grooved to 
retain the oil and carry it over the shaft. The 
bearings are provided with sight feed oil cups, or 
are made self-oiling in some sizes of machines 
when preferred. 

The rocker arm is of cast-iron, supported on a 
projection of the pedestal. In the centre a hole is 
drilled and tapped, into which a handle for turning 
the arm is secured. This handle passes through 
the arm, and when screwed up, its head is buried 
in the standard so as to hold the rocker arm firmly 
in any desired position. To shift the brushes it is 
only necessary to unscrew the handle which 
loosens the rocker arm, when it can readily be 
turned in the desired direction. 

The brush holders are made of brass, supported 
on brass rods, secured to the rocker arm by nuts, 
which are insulated with hard rubber washers and 
bushings. Any desired tension of the brushes can 
be obtained by adjusting the thumb screws in the 
ends of the brush holders. When it is desired to 
raise entirely the brushes from the commutator, 
the holder is simply pushed back until its spring 



130 ELECTRICITY AND ITS 

catches in the slot cut for the purpose. The 
brushes rest between thick metal strips, which 
keep the thin copper strips of which they are made 
up from spreading and yet allow them soft pressure 
on the commutator. 

The brush pins are made so that the direction of 
rotation of motors or dynamos can be readily 
changed by simply reversing the field connections 
and turning the brush-holders around on the pins 
so that the brushes will have the opposite slant to 
the commutator surface. 

An improved form of carbon brush has been 
designed to use with these machines, which in 
many cases has been found preferable to the 
copper brush, and the rocker arm is designed so 
that either kind of brush holder and brushes can be 
used. 

The Crocker-Wheeler Electric Motor, of which 
two illustrations are given, on pages 1 31-132, 
possess some special features of merit which are 
as follows : 

The field magnets are composed entirely of the 
best wrought-iron, each magnet being forged in a 
single piece, and set deeply into the base in order 
to secure solidity and ample magnetic contact. 
The space for wire on these magnets is perfectly 
cylindrical, in the form of an ordinary spool, there- 
by insuring smooth and perfect winding of the 



RECENT APPLICATIONS. 



131 



wire, and is short in length, permitting the shaft 
of the machine to be low enough to free it from 
vibration. By this construction the neutrality or 
freedom of the base from magnetism is secured, 
and there is no tendency to leakage. This is 




THE CROCKER-WHEELER ELECTRIC MOTOR. 



claimed to make the machine much superior to 
those in which the base is made to serve as one of 
the pole pieces, as the bearings then become mag- 
netized and make the shaft bind. 



132 



ELECTRICITY AND ITS 



The armatures contain several improvement a 
They are sufficiently large in diameter to obtain 
slow speed, and are so designed that the wire 
winding is entirely embedded below the surface of 
the iron core, thus protecting it from all injury, 




CROCKER-WHEELER ELECTRIC MOTOR. 



holding it rigidly in position, and rendering it 
possible for the magnets to approach very closely 
to the core, so that an intense magnetic effect is 



RECENT APPLICATIONS. 133 

produced. The armature is mounted upon a brass 
face-plate, which is first turned perfectly true, and 
after completion the armature is very carefully 
balanced, so that when run at full speed the motion 
is hardly perceptible. 

The bearings are all of the self -oiling type, which 
do not require attention oftener than once in two 
to four weeks. 

The base of the pillow-block is hollow, and con- 
tains a supply of oil, which is carried over the shaft 
by two rings which travel upon the latter, and are 
caused to revolve by its motion. They dip in the 
oil and carry it continuously to the upper side of 
the shaft. 

The bushings in which the shaft runs, rest in 
turn in universal or ball joints in seats of babbit 
metal in the pillow-blocks, so that the bearings are 
sure to assume perfect alignment when the shaft 
is introduced. After the motor has run a month, 
the old oil containing the grit, etc., should be 
drawn off from the pet cock at the base of the 
pillow block. This cock should then be closed and 
fresh oil introduced by removing the thumb screw 
in the pillow block cap on top. 

The brushes are held by rocker arms which can 
revolve freely around the entire circle, without fear 
of the brass connecting parts " grounding" against 
the frame, a great advantage in special work where 



134 ELECTRICITY AND ITS 

motors are to be adapted for use in unusual 
positions. 

With this form of armature core which reaches 
close to the field magnets, and the high grade of 
wrought-iron used for the latter, it is claimed they 
are enabled to maintain the magnetism and there- 
fore the power of these motors, with only about 
one-third as much wire as is used on the fields of 
ordinary standard machines. This great saving of 
wire not only reduces the weight of the machine, 
but materially increases its efficiency, or the 
amount of power that can be obtained from a given 
amount of electricity, for with less wire less elec- 
tricity is required. 

The speed of motors is very low, which in many 
cases makes counter-shafting, etc., unnecessary. 
The proximity of the armature core to the field 
magnets renders a high magnetic pressure 
unnecessary, therefore the magnetism escaping 
from the fields is very much reduced. 

Double insulated wire is used throughout for 
the windings, the cores being first wrapped with 
oiled paper and heavy canvas saturated with shellac. 

The rocker arm is provided with a heavy in- 
sulated handle to enable all adjustments to be made 
without touching the conducting parts, and the 
entire machine is heavily japanned and baked at a 
high temperature, thus securing a polished surface 
which resists dirt and oil. 



RECENT APPLICATIONS. 135 

In connection with their incandescent motors, 
they furnish fire-proof and indestructible regulating 
boxes or rheostats for starting, stopping and vary- 
ing the speed of the machines. These are built 
entirely of slate, china and iron. The arrange- 
ment of contacts in the switch on top of the 
regulator is such that both the field and armature 
of the motor are charged by the single operation of 
turning the knob, making it impossible to put the 
current on the armature before the field is charged, 
which has so often been the cause of the accidental 
burning out of many motors by the use of ordinary 
regulators. 

The field is first charged through a small resist- 
ance coil which is put in for the purpose of pre- 
venting a too sudden change in the magnetic 
strength of the latter, as well as to divide the spark 
when the motor is disconnected. The coils used 
for starting the armature are all of the same size 
wire, carefully tried for carrying the full current of 
the machine at all speeds. With the fire-proof 
regulator, the motor can therefore be slowed down 
and left running at any desired speed, indefinitely, 
and the usual caution " never to leave the box half 
turned on for fear of overheating and fire" is 
unnecessary. 

The Thomson-Houston Stationary Motor. — The 
15 horse-power motor shown in the illustration on 
next page has an average commercial efficiency 



136 



ELECTRICITY AND ITS 



when fully loaded of 91 per cent. This high 
efficiency is obtained by paying careful attention 
to the electric and magnetic proportioning of the 
motor. The magnetic circuit is very short and of 
ample section, and therefore of low resistance, and 




THOMSON-HOUSTON STATIONARY MOTOR. 



the magnetic poles are so formed as to convey the 
magnetism into the armature with the least 
possible loss. As will be noted in the engraving, 



RECENT APPLICATIONS. 137 

the poles of the field-magnets, the bodies or cores 
of which are round in section, project upward, en- 
closing the armature. The armature is nearly 
square in longitudinal section and relatively large 
in diameter. This gives a high peripheral velocity 
and a rapid cutting of the lines of force. In con- 
sequence of this construction, also, the armature is 
capable of exerting a powerful rotative force. The 
armature being short, avoids the use of a long and 
consequently less rigid shaft. The coils of the 
motor-magnet are wound on bobbins which .are 
slipped over the cores ; it is therefore easy to 
change a coil or to replace it for any purpose what- 
ever. The field is wound in shunt to the arma- 
ture, and is relatively of very high resistance. 
This reduces the amount of electrical energy 
required to energize the field-magnet to a very 
small fraction of the total electrical energy 
absorbed by the motor. The armature core is 
thoroughly well built and is a very solid and sub- 
stantial structure. At the same time the perfect 
lamination of the core reduces the loss by Foucault 
currents to a small amount. 

The winding on the armature, which is a modi- 
fication of the well-known Siemens' type, is of very 
low resistance. 

The copper wire on the armature is held in place 
by means of bands, which are made of such 
strength that it is impossible for them to yield 



138 



ELECTRICITY AND ITS 



FfQ J 




n 

■v. 



< 



(jurm*tvr<. Core. 



1 — S. 




BECENT APPLICATIONS. 139 

from the centrifugal force, even when the motors 
are run at abnormal speed. 

Should the reader wish to build a small one-half 
horse power motor he may produce a very good 
machine by carrying out the following directions : 

In designing this motor the aim has been to 
produce a machine embodying a large percentage 
of efficiency, with a reduced percentage of skill 
and labor, and at the same time have a machine 
that will present a neat appearance, as will be seen 
from the general view of the motor. It is mounted 
upon a pedestal, preferably cast of some cheap 
alloy, such as gun metal which will answer the pur- 
pose admirably, whereby it can be set up on the 
floor, the wall or ceiling, or, in fact, any place that 
presents surface enough to fasten it to. The arma- 
ture, Fig. i, is of the Gramme ring type, having a 
winding of No. 1 3 double cotton-covered wire, 6 
turns and 5 layers in each section, making a total 
of 360 turns of wire on the armature. The con- 
nections are shown in Fig. 1. The spider is a 
casting which must be of brass or gun metal, while 
Fig. 2 shows a section of the spider with the soft 
iron wire wound on, which forms the core. After 
winding the wire on, it must be covered with 
paper and thoroughly shellaced, then proceed tc 
wind on the coils as shown in diagram, Fig. 3. 
Figs. 4 and 5 are views of the field-pieces, which 
are of cast-iron and have been designed with a 



140 ELECTRICITY AND ITS 

view to utilizing an amount of the dead wire on the 
sides of the armature, the sides nave purposely- 
been left heavier than the ends of the polar space, 
so that if any irregularities in the winding of the 
armature present themselves there will be stock 
enough to bore out to accommodate it. It is 
advisable, however, to build the armature first and 
then uniformity of the field piece can be obtained, 
as the armature will determine the width it is to 
be bored to and due allowance made in the pattern. 
Figs. 6 and 7 show the bearings, which are of gun 
metal, and being grooved as shown in Fig. 7, to 
accommodate the brush-holder, which is, of course, 
on the commutator end. Figs. 8 and 9 show the 
commutator and method of construction. To make 
the segments procure a casting of copper, bore it 
to fit the sleeve, which is made of hard fibre, put it 
on an arbor and turn it off to the size desired, and 
then cut out short grooves in each segment. Before 
cutting the segments, in performing this operation, 
do not cut clear through while on the arbor, but 
finish with a hack saw. The insulation can be 
procured by turning a fac-simile of the segment 
casting out of hard rubber and sawing into strips, 
which gives an exact reproduction of the segments. 
Fig. 10 shows the studs for the bearing on the 
commutator end, which is of machine steel, the same 
as armature shaft, Fig. 1 1 . Fig. 1 2 is the core for the 
field magnets, made of soft Norway iron. Fig. 13 



RECENT APPLICATIONS. 



141 



$ca.fe oj tttch.es 

1 . l . I i l . 1 . I i I . I . I . 1 . 1 . I ■ I . t ■ 1 . 1 . I . 1 . I . 1 . 1 



> 






o 


1* 


( 




" \ 


----- 




-- 


\ 




) 










142 



ELECTRICITY AND ITS 














RECENT APPLICATIONS. 



143 



is the stud for the bearing on the pulley end of 
machine. Fig. 14 is the washer (made of fibre) 
lor the ends of the magnet-cores, being driven on 
and the edge of the metal riveted down over them 

Fij.13 

OtAc view of Hiotor 




to prevent the wire forcing them off. The wind- 
ing for the field magnets consists of No. 12 double 
cotton covered wire, 36 turns and 6 layers, making 
432 turns on both magnets. This machine is cal- 



144 



ELECTRICITY AND ITS 



culated to develop one-half horse-power at 1500 
revolutions. The connections will be readily 
understood from an inspection of Figs. 13 and 15, 




Figure 15 — End view of motor. 



which show all connections very clearly, a number 
of the commutator connections being left off on 
one side to avoid confusion and to show clearly the 



RECENT APPLICATIONS. H5 

method of connecting. The brush holders can be 
scaled off from these two drawings which is so 
simple as not to need any further detail. On top of 
the motor there i. c ample room f o mount a switch 
board, having two binding posts by which the 
terminals a-a (Fisr. n) may be connected to the 
battery. 



ic 



3 46 ELECTRICITY AND ITS 



CHAPTER VI 



Field magnets. 



The theory of a dynamo requires a coil of wire 
rotating between the ends or " poles " of a magnet. 

In most dynamos there is only one magnet, but 
special forms are made, in which several magnetic 
" fields " or regions are available. Electro-magnets, 
more powerful and compact than permanent forms, 
are almost exclusively adopted. For purposes of 
regulation it is sometimes desirable to vary the 
intensity of these magnets, and electro-magnets 
can be made of any strength by varying the quan- 
tity of current flowing through the encircling 
wires. 

The ends of " field magnets " are usually made 
to embrace a large portion of the revolving arma- 
ture. A permanent magnet can be fitted with 
extensions, as shown in Fig. I. These ends are 
called pole-pieces, as they become the poles of the 
magnet. Five separate pieces are usually joined 
to form an electro-magnet. See Fig. 2. The two 
pole pieces are of cast-iron, the two cylindrical 
"cores" of wrought-iron, as is also the "magnet 



RECENT APPLICATIONS. 



147 



Fi}l 




r~\ 




Fiq 2, 



Z 



N 



Tig A 





< 


J d 







n 9 4 



N 



148 ELECTRICITY AND ITS 

yoke." which connects the cores together. The 
surfaces where these separate pieces touch are 
made very smooth and flat, in order that the mag* 
netic circuit may be as if in only one piece of 
metal. This form is convenient for handling and 
allows easy application of the coils of wire. It is 
not best to wind this directly on the iron, but to 
have it on detachable bobbins. Simple brass rings 
connected with a sheet-iron or tin cylinder is 
strong enough and the spools fit loosely over the 
cores. 

Such arrangements as Figs. I and 2 furnish 
magnets with "salient" poles, that is, virtual poles 
at the very ends of the cores. If another set of 
cores be added to the other side of the pole pieces 
(Fig. 3) a field of twice the strength can be 
obtained. In this case the poles are "consequent," 
for the magnetism is available in pole pieces, 
which are interruptions in the otherwise continuous 
ron. 

Sometimes only one coil of wire is used, and 
consequently but one core is necessary. Fig. 4 
shows one position, and Fig. 5 the same with the 
core perpendicular. When this form is doubled it 
becomes Fig. 6. By lengthening the pole pieces 
into cores this form becomes merged into Figs. 7 
and 8. 

Just which form of these field magnets is best to 
use depends on the purpose for which the dynamo 



EECEXT APPLICATIONS. 



149 



Tin 5 



Tw 6 



- ! 




\r \! 


! s 



V 



rz s_ 



Fi 9 7 




I'tij 8 



N 



5 



u 



150 ELECTRICITY AND ITS 

or motor is designed. Sometimes, for the same 
purpose, different forms work equally well- Usually 
dynamos for continuous currents have but two 
poles, as shown in these figures. By increasing 
the number of poles the armature will receive the 
desired number of inductions at a slower speed ot 
rotation. An alternating current machine should 
have a large number of poles in order to give a 
rapid alternation. Two hundred and fifty reversals 
per second is commonly attained. 

Fig. 9 shows a four-pole magnet. The cores are 
also used as pole pieces. Fig. 10 shows a six-pole 
magnets. This can be used for continuous currents 
but is better adapted for alternating. It is not 
unusual for an alternator to have 16 or 20 poles. 
For future machines the promise is for even a 
larger number. The more poles the slower the 
speed can be, and the tendency now is toward slow 
running machines. 

For arc dynamos the mass of iron in the mag- 
nets should be comparatively small, but a large 
amount of copper wire needs to be used on the 
spools. Arc dynamos are series-wound, that is, the 
entire current from the armatures circulates around 
the field cores; the field is in " series" with the 
rest of the circuit. When this winding is used the 
field magnet experiences every fluctuation of the 
current that lights the lamps, and this varying 
magnetism is utilized in adjusting the regulator. 



RECEXT APPLICATIOXS. 



151 



An arc dynamo preserves a current of uniform 
strength, but the potential or voltage varies accord- 
ing to the number of lamps supplied. 

A dynamo for incandescent lighting or for 
supply of power should have a constant voltage, but 
strength or quantity dependent on the demand. 
For such a machine there should be a very massive 
field magnet. The winding should be in "shunt," 



Tig. 9. 



Tip 10. 





that is, the field spools should be in a circuit, inde- 
pendent of the working circuit. This subtracts so 
much from the useful output of the machine, but 
the wire is fine and long and is of sufficient resist- 
ance to allow only about one one-hundredth of the 
whole current to pass. The magnetism thus kept 
nearly constant, the potential is uniform, 



152 ELECTRICITY AND ITS 

Absolutely constant potential can be obtained 
by " compound" winding; that is, by putting both 
series and shunt coils on the magnet cores. Such 
winding is in common use on dynamos, for almost 
all work except arc lighting. 

To get just the amount of wire on a field magnet 
is not easy without elaborate data. Manufacturers 
usually wind a temporary coil on each bobbin for 
experimental purposes/ The armature is driven at 
its calculated speed and current from another 
source sent through the temporary field wire. 
From measurements of the number of turns of 
wire and the current necessary to bring the 
machine to its proper output, the final winding can 
be calculated. It is desirable to use as large wire 
as possible in order that the heating effects be low. 
About iooo amperes to the square inch of cross 
section of wire is a safe allowance. For arc 
dynamos the wire needs to carry about 10 amperes. 
From one to three amperes is in the field circuit 
of a shunt dynamo. In compound machines the 
shunt is the same as in the previous case, but the 
series coil needs to be sufficiently large to carry 
perhaps several hundred amperes. 

A dynamo should be designed in such a manner 
as to economize material. The iron of the magnet 
should also be compelled to form the frame for the 
machine, and give places for the armature bearings. 
No part of the magnetic circuit should have less 



RECENT APPLICATIONS. 353 

cross section of iron than the cores. This rule has 
not always been observed, and a large amount of 
external magnetism, or leakage, has been the re- 
sult. A perfect dynamo would exhibit no outside 
magnetism, all being used within for useful work. 

The size of field magnets is dependent on the 
armature. The capacity of a dynamo lies in its 
armature, and for that the first calculation is made. 
Afterwards suitable fields are designed. An early 
error in dynamos was to use very long cores ; at 
present they are very short and the magnetic yoke 
massive. The diameter of the cores for most 
purposes should be two-thirds or four-fifths of the 
armature diameter, and length about equal to the 
diameter of armature. 

An important consideration in the design of 
magnets is to keep in mind accessibility to the 
armature. It is not advisable to remove or replace 
an armature endwise, but the field magnets, in part 
or whole, should be easily removed and leave the 
armature open for inspection or removal. 

In the next chapter, which discusses armatures, 
general dimensions will be given, and suitable 
forms of field magnets suggested which correspond 
with present electrical practice. 



lo4 ELECTKICITY AND ITS 



CHAPTER VII. 



ARMATURES. 



The sight of a keeper across the " poles " of a 
horse-shoe magnet is familiar to every one. Such 
a piece is also called an "armature." Every dyna- 
mo has an armature, yet the form of it is such as 
to conceal its identity. Its purpose is the same — 
to convey the magnetism from one pole piece to 
the other. Instead of being flat or cubical, arma- 
tures are cylindrical, and have imbedded in them, 
or laid upon their surface, copper wires for con- 
ducting the currents of electricity that are gener- 
ated when the armature revolves. 

By means of commutators, to which the wires 
are connected, the currents are collected by brushes 
and carried away tor light lamps or for any other 
purpose. 

The iron centre upon which the wire is wound is 
called the core. 

One of the earliest armatures is the Siemens' 
or shuttle form. A cylinder of wrought or 
annealed cast-iron is grooved on both sides and the 
recesses filled with wire wound back and forth. 



RECENT APPLICATIONS. 



155 



To each end is screwed a brass head, in which 
short shafts are fitted. These shafts, besides sun- 
porting the armature in position, carry the driving 
pulley and the commutator. 

The commutator has but two parts, to which, 
after being carried through a hole in the shaft, the 
two ends of the coil are attached. Fig. i shows 
side view of this construction, Fig. 2 a transverse 
section with wire enlarged, and Fig. 3 the commu- 
tator. 



L 




Figure i. 

This form of armature is very energetic and is 
well adapted to small dynamos for intermittent 
work. For experimental purposes a large current 
is available for short periods. When run continu- 
ously this form heats greatly on account of the 
large mass of iron in the armature. 

The rapid magnetizations and demagnetizations 
generate wasteful heat currents. By building the 
:ore of sheet iron, separated by tissue paper, the 
heating can be reduced. Each sheet is made the 
shape of Fig. 2, and strung along on a shaft that 
extends entirely through, in one piece, from pulley 
to commutator. In this the core is subdivided 



156 



ELECTRICITY AND ITS 



into such a large number of small masses that the 
eddying heat currents are considerably obviated. 
A core one and one-half inches in diameter and 
four inches long, made in this way and wound with 
No. 1 8 wire, will furnish a current of about 25 volts 
and 4 amperes. For such an armature fields of 
form in Fig. 2 or 3 of last chapter, but with cores 
of flattened sections instead of circular will be 
suitable. 



fzyz 



ftf 3 





As there is but one coil of wire on this core, 
there will be but two inductions of electricity for 
every revolution. This would give seven pulsations 
instead of a smooth flow of current. Instead of 
two large grooves for the wire, a larger number of 
small grooves can be cut in the core, and each 
have its own coil of wire. Such an armature is 
used in many makes of dynamos. It has the value 
of keeping an excellent magnetic path from one 
pole piece to the other. The wires are securely 



RECENT APPLICATIONS. 157 

held in place and well protected from damage. 
See Fig. 4. 

Any armature which has projections of the core 
between the coils, heats itself and the pole pieces. 



FioA 



Tig 5 





Most manufacturers make the core perfectly 
smooth and wind the wire over the entire surface. 
See Fig. 5. The sheets of the core are strung on 
a shaft, tightened between two wrought-iron"heads" 
screwed on the shaft. These heads are slotted to 
receive wooden or leatheroid pegs, which keep the 
wires in place. With such armatures very many 
different coils of wire can be put on and supply a 
current of almost absolute continuity. 

A core four and three-eighths inches in diameter, 
six inches long, wound in thirty-two sections with 
No. 1 5 wire, would supply a current of 80 volts and 
15 amperes. 



158 ELECTRICITY AND ITS 

This is a conventional form of armature, and 
almost any style of field except the "multi-polar" 
is suitable, if the right proportions are observed. 
Twenty pounds in all of No. 23 wire would be 
required for the field spools. Two horse-power 
would drive such an armature. By increasing these 
dimensions in proportion any size desired can be 
reached. One of twice these dimensions would 
furnish eight times the capacity. Four times the 
dimensions would give sixty-four times the capacity. 

In such armatures the coils are not kept entirely 
separate from each other, but coil after coil is put 
in place so that the end of one coil and the begin- 
ning of the next is united and, besides, furnishes a 
connecting wire for a segment in the commutator. 
The winding can be with one continuous wire, with 
branches at equi-distant points for the commutator 
segments. 

The last form has been called the cylinder or 
drum armature. In i860 Pacinnotti invented a 
ring armature. The winding was between projec- 
tions on the outside of the core, but was threaded 
in and out through the inside. See Figs. 6 and 7. 

At first a solid piece of iron was used to form 
the core, but, as in other cases, sheet iron is now 
exclusively used. 

A good proportion for cylinder armatures is for 
the diameter to be two-thirds the length. In the ring 
form the diameter should be about twice the length. 



KECENT APPLICATIONS. 



159 



Gramme, in 1870, modified the armature by 
leaving off the projections and winding wire over 
the entire outside surface, as has been done in the 
case of the drum form. 




The early manner of holding this core was by 
means of two taper plugs of wood forced into the in- 
side by nuts on the shaft. See Fig. 5. This injures 
the insulation and prevents the ventilation of the 
wire. Besides, it is difficult to wind the wire 
evenly enough on the inside of the ring to make 
the armature run true. See Fig. 8. 

In American practice the sheets have notches, 



160 



ELECTRICITY AND ITS 



n 9 ? 




into which slip arms of two "spiders." See Figs. 
9 and 10. These are of brass and firmly keyed to 
the shaft. Stiff wrought-iron rings at the ends of 
the armature core receive the pressure of the spiders 
and hold the sheets firmly together. The wire is 
threaded in and out as in the other case, to make a 
continuous winding around the ring, with branches 
at necessary places for the commutator segments. 

When an accident occurs to a cylinder armature 
it is usually necessary to take off all the wire to 
get to the damaged coil. With a ring core one coil 
is not encumbered with others on top, and it is not 
a serious matter to take out and replace one coil 
without disturbing the others. 

As in the case of drum armatures, a safe calcula- 
tion is I volt for every 2 feet of active wire. Very 
small machines are not so efficient as large ones. 
Acore 7 inches in outside diameter, 5 inches in- 



RECENT APPLICATIONS. 161 

side, and 4 inches long, wound in 48 sections 
with No. 1 5 wire would furnish a current of 80 
volts and 15 amperes. The wire should be two 
layers deep, and the armature driven at about 2,200 
revolutions per minute. 




A field magnet of style of Fig. 1 or 8 would be 
suitable. By using wire of one-half the size and mak- 
ing twice as many turns, a four pole field ( Fig. 9 ) 
could be used. Twelve pounds of No. 12 wire 
would be sufficient for the field spools. The same 
shunt winding as used for the drum armature 
would serve if desired. 

For mechanical considerations the speed of an 
11 



162 



ELECTRICITY AND ITS 



armature should be kept low ; the ring form, with 
its large diameter gives requisite peripheral 
velocity without unduly heating the bearings. 

Those armatures just described are designed for 
furnishing continuous currents. A dynamo always 
generates currents in alternating directions. Com- 
mutators are used to direct them all in the same 
direction. An alternating current may be consid- 
ered as in the more natural primitive state. 

FtfJ. 




If in Fig. i the ends of the coil were carried to 
two separate rings and a brush bear on each, an 
alternating current could be obtained. As there is 
but one coil, the alternations would be too infre- 
quent for most purposes. To multiply these pul- 



KECEXT APPLICATIONS. 



163 



FlJ 10 




saticns, armatures are made with many coils and 
the field magnets with an equal number of pole 
pieces. If coils are wound in the shape to fit the 
armature of Fig. I and 2, but slipped over the pro- 
jections of the core of Fig. 3, so that each may fill 
one-half of two adjacent grooves, or spaces, a com- 
mon arrangement for an alternating armature will 
result. All the coils are connected in series, and 
the ends carried to two collector rings. When the 
core has no projections the coils are simply laid 
flat on the surface, held in position by pins and 
wrapping wires. The ring core is best adapted to 
alternating current dynamos, as the radial mass 
of iron is small, consequently will heat least, yet 
give a high peripheral speed. Usually the fields 
must be separately magnetized from a small con- 
tinuous current machine, but it is possible to make 
u self-exciting alternators. " 

Extreme care must be observed in preparing an 
armature core for winding. All corners are to be 



164 ELECTRICITY AND ITS 

well rounded, so as not to cut through insulation. 
Several layers of paper, canvas, or mica, well 
shellaced together, are put on smoothly. The 
ordinary insulation on wires is not sufficient where 
they cross each other, but in addition must be 
carefully wound with tape. After winding, the 
armature should be balanced with sheet lead, and 
then the wrapping wire, well separated from the 
copper winding, put lightly on in narrow bands. 
Wires leading to the commutator segments should 
be large and well insulated. 

Properly made there is no electrical difference 
between the drum and ring forms for armatures. 
Where a narrow machine and high speed is desira- 
ble the drum form is best ; while for a short shaft 
and slow speed the ring offers valuable advantages. 



RECENT APPLICATIONS. 165 



CHAPTER VIII. 

THE TELEGRAPH AND TELEPHONE. 

The telegraph instrument now most commonly 
used is the Morse instrument. It consists of an 
electro-magnet which, when a current is made to 
pass through its coils draws down an armature for 
a long or short time as the operator may wish. 
This is done by simply pressing down a key for a 
correspondingly longer or shorter period of time. 
This armature and electro-magnet is called a 
sounder. On page 166 will be found an illustra- 
tion of the Morse instrument, for the use of learn- 
ers, connected with one cell of battery, and on page 
168 will be found an illustration of the relay. 

If the reader will study the diagram, Figure I, 
he will be able to understand the wiring and 
operation of a telegraph line. 

Both sets of instruments are identical ; indeed 
if other stations are inserted between the terminal 
of the line, there is no alteration. When no mes- 
sage is being sent, the switch //, beside the "key" 
g is kept closed. Then the circuit is not broken, 
and when any key is depressed, all the receivers 



166 



ELECTRICITY AND ITS 




RECENT APPLICATIONS. 167 

throughout the line receive the impulse. As the 
current in a telegraph wire is exceedingly small, 
delicate apparatus alone can record the passage of 
the current. Usually the flow is too weak to work 
a " sounder, " so a " relay " b is inserted. The mag- 
net in this is very sensitive and simply attracts a 
delicately balanced armature, c, that is held away 
normally by a slender spring. On this armature 
is a finger that makes contact with the screw d, 
when a current is flowing through the coils of b. 
This contact closes a local battery (/) circuit, 
which is sufficiently strong enough to operate the 
sounder e. 

Line batteries i are needed at one end only, if 
there is good insulation on the poles. Local bat- 
teries / to work the sounder must be at every re- 
ceiving station. 

With a short line the relay magnets and local 
batteries can be dispensed with, and the line bat- 
teries connect directly with the sounders. 

Should the reader wish to construct an experi- 
mental instrument, he may do so by working out 
the following directions. 

The cores of the magnets are to be made of | 
inch round wrought iron — Norway iron preferable, 
on account of its great purity and softness. Cut 
two pieces I \ inches long and tap one end of each 
for a I inch machine screw. Fit over each end of 
each of them a washer made of fiber or ebonite, 



168 



ELECTRICITY AND ITS 




RECENT APPLICATIONS. 



169 



I inch in external diameter and \ inch thick ; they 
must fit tightly. Insulate the cores between the 
washers and bore a ^ inch hole in one washer on 
each spool to take out the beginning wire and 
then put the spools in a lathe and wind them full 
of No. 24 insulated wire. It is customary to 
slip over the spool when the winding is finished 
a casing of ebonite both as a protection to the wire 
and to improve the appearance, but this is not 
essential. 




TELEGRAPH SOUNDER. 



The yoke is also soft iron | of an inch wide, -ft 
of an inch thick and i| inches long. Drill a | inch 
hole in each end, i^ inches distant from each other 
and one in the middle tapped for a j% inch screw 
thread. Screw the spools you have wound to the 
yoke making a u shaped electro-magnet. This 
magnet stands on a base made of \ inch sheet 
brass, 2\ inches wide and 5 inches long. Drill a 
! 3 6 inch hole through the base 2\ inches from 
one end and midway between the sides : this hole 



no 



ELECTRICITY AND ITS 



■i 






U 



g 







"A 

1 — ®@h§>@>© — P 



RECENT APPLICATIONS. 171 

is for the purpose of screwing the magnet to the 
base. Cut a strip of J inch sheet brass ! 5 6 of an 
inch wide and ioj long; bend it into a u shape, 
making the curved portion a semi-circle of 2 inches 
diameter ; at 2 inches from each end drill and tap 
a hole for a \ inch screw. 

Now file a groove in the edges of the two sides 
of the base-plate, i 5 6 of an inch in width, and \ of an 
inch deep, the edge of the groove to be i^- inches 
from the end of the plate the magnet is nearest. 
The legs of the u piece fit with this groove and are 
to be secured to the base with ^ machine screws. 

The anvil had best be cast from brass, making a 
pattern for the same from Fig. 2. The bottoms of 
the legs of the anvil are to be tapped for 3 8 2 ma- 
chine screws, and holes drilled in the brass base 
through which to pass the screws from underneath 
and secure the anvil. The straight leg should be 
3 inches from the end of the base, and toward the 
magnet, as shown in the drawing of the completed 
instrument. The hole in the short arm is \ of an 
inch from the end, and is drilled and tapped for a 
\ inch screw. 

Another brass piece which should be cast from 
brass, should be made in accordance with Fig. 3. 
The holes y and z are to be drilled and tapped for 
a I inch screw, and x drilled with a No. 30 drill. 
Through the hole in the little downward projection 
of this piece is to be driven a piece of No. 14 



172 



ELECTRICITY AND ITS 



Stubbs' steel wire, pointed at each end, and well 
hardened. 

A soft iron armature of the shape and dimen- 
sions shown in c> Fig. 3, is screwed on the upper 
side of the brass casting, to the hole y. Four 
thumb screws and check nuts will be required, and 
may be made by following the dimensions given at 





ua 4 




jl; 






•i 

•85 

1 


5" 




' 1-^" 






'* 




({ 


^\ 



~* 



cO|oD 

0* 



*5* 
*16 



Figure 2. 



#, Fig. 3. Two of the thumb screws should have 
their ends slightly countersunk or drilled with a 
very fine drill, to form bearings for the pointed 
ends of the Stubbs' steel pivot. Two more screws 
and nuts are needed : the screw to be made from 
I inch brass wire, 1 inch long, and threaded the 



RECENT APPLICATIONS. 



173 



entire length, and the nut to fit this thread. 
Through one end of this screw drill a small hole. 
At f of an inch from the end of the base plate, 
and directly under the projecting end of the arma- 
ture carrier back of the pivot, solder a small hook. 
Make a closed spring out of No. 22 spring brass 
wire. We are now ready to put the machine to- 
gether. 



i&- — * — r — *— i K - — *i 



&», 







£5U 




&*i 



I 3 



m ft 3 



Figure <, 



In the first place, the brass base-plate should be 
mounted on a neat wooden base, a little larger 
than the brass plate, and on the wooden base place 
two binding posts. Screw the magnet to the base- 
plate, if you have wound both cores in the same 
direction and have screwed them to the yoke so 
that both starting ends are together, connect the 
two inside wires together and the remaining ends 
to the binding posts, on in other words, see that 



174 ELECTBICITY AND ITS 

the wires are connected in such a way chat if the 
magnet were bent out straight, the current 
will pass around the bar in one direction through, 
out its whole length. Screw the anvil to the base 
plate and put in the adjusting screws and nuts as 
shown in the general drawing. 

Place the armature in position and adjust it so 
that it moves easily on the pivot point by means of 
the adjusting screws in the sides of the u shaped 
piece. Put the nuts on the piece of threaded wire 
you made and slip it into the hole in the end of the 
armature. The end with the hole in it should be 
down, and into the hole hook one end of the spring 
you wound, and cut off the other end so that it will 
reach the hook beneath with a little stretching, 
and hook it there. The tension on the spring can 
then be regulated by the nuts on top, and should 
be such that the armature will be pulled against 
the top stop when freed. 

Adjust the screws in the anvil so that the arma- 
ture will have \ of an inch play between them, and 
at its lowest point the soft iron piece will be £% of 
an inch from the ends of the magnet, and your 
sounder will be ready for work, that is to say, 
whenever you put a current through the coils the 
armature will draw down and make a click, and 
when the current is taken off, will fly up and make 
another. 

The place in which the instrument is set makes 



RECENT APPLICATIONS. 



175 




TELEGRAPH KEY. 



..-*. 



o 
o 




*c< 



Figure 4. 

a good deal of difference in the sound. A sound- 
ing board of some sort is necessary if it is desired 
to have the instrument make much noise. A 
good table answers for this very well, and often 
the instrument is placed upon a plate of glass or 
has a bell or curved piece of tin attached to the 
anvil for the purpose of increasing the volume of 
sound. The Morse Alphabet is given below, 
abcdef g h 



m 



w 



& 



10 



t r id ELECTRICITY AND ITS 

To break and make the circuit and thus work 
the instrument, we must have a key which can be 
made from a piece of spring brass, as shown in 
Fig. 4. 

Cut and bend the brass in the shape shown, and 
screw a wooden or ebonite button to it. The 
screw head on the under side is to be filed off a 
little flat and another screw placed beneath, so that 
its head may be touched by the other when it is 
pressed down. The wires are to be connected to 
the strip and screw head as shown, though of 
course this is to be done underneath the board on 
which they are mounted, so that the wires will not 
be seen. The circuit must be kept closed except 
when a message is being sent, so another strip of 
brass is to be screwed to the first, so it will move 
freely and will close the circuit when swung 
against the lower contact. A suitable handle is to 
be made for this. 

The contacts of the key are apt to become fouled 
by the dirt and sparking on breaking the circuit, 
and must be occasionally cleaned. The fouling 
from the last cause can be obviated somewhat by 
soldering small pieces of platinum to the contacts 
as it does not oxydize as readily as most other 
metals. 

THE TELEPHONE. 

Electrically speaking the telephone is a very 
simple piece of apparatus. A coil of fine wire 



RECENT APPLICATIONS. TiT 

upon a permanent magnet in front of a plate of 
thin iron is the essential requisite. 

The vibrations of the thin plate, which follow 
those of the air, alter the distribution of the lines 
of magnetic force around the coil and set up in it 
electro-motive forces and therefore currents corre- 
sponding to these vibrations. 

These currents carried to a similar instrument, 
will cause its diaphragm to vibrate in a like man- 
ner, and set up sound vibrations in the air near it. 
The magnet should be long in proportion to its 
diameter in order to retain its magnetism to any 
considerable degree, \ of an inch diameter to six or 
seven inches long will be a good proportion. It 
must be of the best tool steel, hardened glass, hard 
and strongly magnetized. The best steel is what 
is known as Tungsten steel, which has the property 
of retaining magnetism to a marked degree. 

The wire used is silk covered copper about No- 
36, and is wound into a spool, made by placing two 
discs of thin hard wood upon the end of the mag- 
net, a quarter of an inch apart. The space be- 
tween them must of course be insulated by wind- 
ing a thickness of paper on the bare iron. 

This spool is to be wound full of wire. See 
Fig. 1. 

For a case turn up a piece of wood the length of 
your magnet, 3 inches in diameter at the large 
end, and 1 inch at the small end, and with a cavity 
12 



178 



ELECTRICITY AND IT* 



in the large end 2 inches in diameter, and | inches 
deep. 

Bore a hole through the centre from end to end 
just large enough to allow the magnet to slip 
through and for a set screw to hold it, put a wood 
screw in one side near the end as shown in 
Fig. 2. 




Figure i. 

The lead wires can be taken out of the sides of 
the large end of the case or can be passed through 
the handle and out at the end, as is customary with 
the shop made article. The last is of course the 
neatest way but is not always convenient. 




Figure 2. 
These wires should be passed into the inside of 
the box and there soldered to the fine wires from 
your coils. On the outside they should terminate 



RECENT APPLICATIONS. 



179 



in small binding posts, so as to prevent the possi- 
bility of their being worked about and breaking 
off the fine wires. 

A cap should now be turned up to fit the large 
end of the case, something like the adjoining sec- 
tional sketch — Fig. 4 — and screwed to it through 
the flange. 

The diaphragm can best be made of a piece of 
"tintype " plate which can be procured from any 
photographer. 




Figure 4. 
A piece of ordinary thin tin plate would answer 
but the other is better, Cut the plate to a circle 
the same diameter as the large end of the case and 
punch holes where the screws come, and screw it 
down under the cap to the case. You must of 
course have two such instruments, if you intend to 
carry on conversation and these will answer for 
both transmitter and receiver. Adjust your mag- 
nets by removing the cap and slide the diaphragm 
partly off, so you can see the magnet beneath, and 



180 



ELECTRICITY ANP ITS 



slide this in or out until it clears the plate by ^ °f 
an inch, and hold it in rhis position by the set 
screw. 

Replace the diaphragm and cover and connect 
your two instruments by two wires. You are now 
ready for conversation, which there should be no 
difficulty in maintaining, if everything is properly 




Figure 5 



made and there are no breaks in your fine wire coil. 
This is a point that must be looked after carefully 
as breaks are very likely to occur with such small 
wire. 

The telephone is put to other uses besides the 
transmission of speech, chief among which is the 
detection of minute currents of electricity. This 



RECENT APPLICATIONS, 181 

is done by making and breaking the circuit with 
the telephone in it generally by some form of in 
terrupting device or buzzer, when of course if a 
current is flowing, its presence is indicated by 
clicks of the diaphragm. 

Another use is in connection with the micro- 
phone to enable one to hear very faint sounds. 
The microphone is simply two pieces of carbon 
placed in light contact with each other upon a 
sounding board. A simple form is shown in 

Fig- 5- 

Two pieces of willow charcoal are held in the 
spirals of two brass wires, which can be moved i^ 
and down the wooden standard. 

Between them is a pointed piece of charcoal 
which rests in a hollow in the lower piece and 
touches the upper one very lightly. The wires are 
attached, as shown, so as to include a battery and 
telephone in the circuit, and if the box used as a 
base is made of thin wood very slight sounds 
may oe heard, which originate upon it. Perhaps it 
would be well to say that until 1893 — patents 
cover the use as well as the manufacture of the 
telephone. 



182 ELECTRICITY AND ITS 



CHAPTER IX. 

ELECTRIC BELLS HOW MADE, HOW USED. 

An electric bell in common use consists of an 
eiectro-magnet having an armature to which is 
attached a small hammer, so arranged that by 
sending a current through the circuit the armature 
is made to vibrate and the hammer beats against a 
gong. The bell is usually operated by a battery, and 
the circuit may be closed by simply pressing a small 
push button, thus causing the current to flow along 
the line and around the coils of the electro-magnet, 
which draws the armature toward it. A contact 
breaker consisting of a spring tipped with platinum 
which rests against a platinum tipped screw is 
attached to the armature. This makes and breaks 
the circuit which causes the hammer to beat 
against the gong and then fall back against the 
screw which immediately closes the circuit again, 
causing the armature again to be attracted toward 
the magnet, and so on. In fact an electric bell is a 
miniature electric motor. For the benefit of the 
reader who wishes to construct an electric bell the 
following directions are given. 

The appended sketch will give a general idea of 



RECENT APPLICATIONS. 



183 



the construction of the beli. The magnet as wil 
be seen is simply a single coil of wire and is sur 
rounded by a sheath of soft iron which forms on s 
pole while the core of the magnet forms the other. 
Make the core of a piece of good soft round iron 
I of an inch in diameter and 2\ inches long and to 
one end attach, by a screw or by welding, an iron 




disc i J inches in diameter and | of an inch thick. 
On the other end place a tight fitting washer 
of fiber or hard wood I J inch in diameter and \ 
inch thick, forming thus a spool on which to wind 
the wire. See Fig. 2. 

Insulate the iron parts carefully with paper shel 
laced on where the wire will touch it and after drill- 



1-S4 



ELECTRICITY AND ITS 



mg a hole in the fiber washer near the core to take 
out the starting end, wind on the wire tightly and 
smoothly. Use for this purpose No. 24 cotton-cov- 
ered copper wire and wind the spool up nearly even 
with the fiber washer and take out the end of the 
wire. Wind a strip of paper on top of your wire 




Figure i. 

until you have a cylinder of the same diameter as 
the washer, and shellac it fast. Your iron disc 
should now project ^ of an inch all round. Now 
turn up a wooden cylinder the same size as the 
outside of the winding you have just completed 
and use this as a form on which to make the iron 



RECENT APPLICATIONS. 185 

sheath. Take a strip 2§ inches wide of soft sheet 
iron, such as is used in making stove pipes, and wrap 
this tightly around the form until its outside diam- 
eter equals that of the iron disc. 

If you have facilities for doing so, sweat the end 
of the strip down to the turn beneath it, otherwise 
you will have to wind on it several turns of wire to 




Iron 



Figure 2. 

keep it from untwisting like a watch spring. Slip 
this sheath over the coil and up tight against the 
disc and wedge it there by small pieces of paper. 
Make the armature of a piece of iron about ^\ of 
an inch thick and cut it in the form shown in 
Fig. 3, the larger circle having the same diame- 
ter as the outside of the sheath and the smaller 
one being about \ of an inch in diameter and 
twisted so that its plane is at right angles to 
the plane of the other, as shown in the general 



186 



ELECTRICITY AND ITS 



drawing. The length of the neck between them 
will depend somewhat upon the way you arrange the 
different pieces, the size and shape of the bell, etc., 
and it had better be measured for when all the 
other parts are in place.* 

Make the spring of spring brass about 3 X of an 




Figure 3. 





Figure 4. 



Figure 5. 



!nch thick and \ of an inch wide and shaped as in 
Fig. 4. It is to be fastened by its foot to the under 
side of the base board so as to give it a long lever 
arm, and brought up through a hole as shown in the 
general drawing. Rivet it to the armature by at 
least two small rivets. Its extension above forms 



RECENT APPLICATIONS. 



187 



the contact spring which must be filed down thin- 
ner than the rest and have a small silver contact 
piece soldered to it. Make the other part of the 
contact of a piece of sheet brass about r ^ of an 
inch thick, cut and bend it as shown in Fig. 5. 
The slot in the middle of the broad end serves 
to adjust the contact distance, when a round head 
wood screw passes through it into the board. 



1 



U 



i- 



u 



0H0 



O 



* 



u 



Figure 6. 

We are now ready to assemble the pieces 
Mount the magnet in a block and fasten it down 
by a band of sheet brass or tin, as shown in the 
general drawing. Fasten this block to a base board 
and cover the magnet with a small box, (this is 
shown broken away in Fig. 1), with one end open. 
The open end (that is, that with the fiber washer 
on it,) of the magnet must project slightly from 
this end of the box. Place the armature in posi- 



188 



ELECTRICITY AND ITS 



tion in front of the magnet leaving about 3 3 2 of an 
inch clear space between them. Attach your gong 
to the top of the box where it will be struck 
by the clapper when the armature is drawn up. 
The general drawing shows the method of con- 
necting up, and when these connections are prop- 
erly made and a battery inserted in the circuit, the 
bell should ring vigorously. 

Of course some judgment must be used in 
making the adjustments, that is, the contact piece 




and spring must touch lightly when in a state of 
rest and must break circuit when the armature is 
attracted by the magnet and before it strikes the 
bell. 

Some different ways of wiring bells are shown 
on pages 187, 188 and 189. 

Fig. 6 shows bells in multiple actuated by one 
button. Fig. 7 shows one bell actuated by three 
different buttons. Fig. 8 shows three bells in 
multiple actuated by three different buttons. 



RECENT APPLICATIONS. 



189 



The description of these three simple ways of 
wiring is given to help the reader to understand 
or enable him to do such simple wiring as he may 
want to do at home. Of course it is not to be sup- 
posed that he could do a complicated job of work, 




v.., 



e> 



1 



HI! 



.j 



i • 







Figure 8. 



such as wiring hotels or large factories where a 
large number of bells would be required, but for 
ordinary work the writer thinks a careful study of 
the diagrams will enlighten the reader sufficiently 
to assure his success in ordinary work at home. 



190 ELECTRICITY AND ITS 



CHAPTER X. 

HOW TO MAKE AN INDUCTION COIL. 

Procure a piece of hard rubber, bore and turn 
it to dimensions and shape given in Fig. I ; drill 
two small holes about i e diameter in the flange on 
one end, then drive on an arbor — not too tight — 
and proceed to wind on two layers of No. 15 
double-covered cotton wire ; this is called the pri- 
mary coil. 

The terminals of this coil are to be brought 
through the two holes previously drilled in the 
flange ; fasten the wire inside the flange by stout 
thread that has been placed underneath the first 
layer having the ends left hanging out. Now 
shellac this wire all around and neatly put on a layer 
of stout paper and shellac. For the secondary or 
outside coil, use No. 26 or 30 double-covered wire; 
put on about eight layers and fasten to the oppo- 
site end of the spool in the same manner as the first. 
Bring the terminals, one on each side of the coil, 
down close to the inside of the flange in a neat coil 
and thence to the binding posts shown in Fig. 7 A, 
and the secondary coil is connected complete. 



RECENT APPLICATIONS. 



191 




192 



ELECTRICITY AND ITS 



The next object is the circuit-breaker, which is 
made from a piece of soft Norway iron ; turn it 
with a shoulder as shown in Fig. 2. Make two 
washers — Fig 3 — out of fiber or hard rubber, 
slightly counter-boring one to conform to the shoul- 
der left on the iron core and have thern driven on 
tightly, up at the opposite end of the core with a set 
chisel to prevent the wire forcing the washer off 




fjj & 



t 

/ 3Z 



2: 




/ 



J 



I* 1 *** 



+£ 



y« 



from that end, and cover the core with stout paper 
cemented on by shellac. Now wind on three layers 
of No. 15 wire having a terminal at each end of the 
coil ; fasten the wire at each end in the manner 
described and at the end shown in Fig. 7 B; bring 
the wire down through the board which has previ- 
ously been grooved to receive it and connect it to 
the spring of the circuit-breaker by a screw and a 
nut as shown in Fig. 7 B — the nut being underneath. 



RECENT APPLICATIONS. 193 

Make the spring from a piece of thin German 
silver, and attach, by means of a rivet or some sol- 
der, a small piece of soft iron at the end. Bend 
the end which rests on the board and drill two 
holes in it having the one nearest the upright posi- 
tion of the spring considerably larger than the 
screw which will be used to fasten the standard — 
Fig. 4 — to the board. The reason for so doing is 
to keep the screw from forming a contact with the 
spring which would make a short circuit and pre- 
vent the coil from working ; for the standard, use 
|-inch soft brass which can be easily bent. Drill 
and tap the hole for the knurled screw which is 
about 10 — 24. 

The standards to support the coil of the circuit- 
breaker — Fig. 5 — can be made of ^-inch sheet 
brass and fastened to the board, being bent inward 
at more than right angles, they will hold the coil 
very secure when it is forced in between them. 
Now the connections can be made and by a study 
of the assembled view these can be readily com- 
prehended. It will be perceived that the coil of 
the circuit-breaker is placed in the same circuit 
with the primary coil. This is accomplished by 
bringing the lower terminal of the primary coil and 
the terminal of the circuit-breaking coil through 
the board as shown, and connecting them under- 
neath, while the opposite terminal of the circuit- 
breaking coil also is brought through the board and 

13 



194 



ELECTRICITY" AND ITS 



FjJ& 






£3 




^ 



RECENT APPLICATIONS. 195 

connected to the vibrating spring, which in its turn 
along with the adjusting screw standard is fastened 
on the board at a proper distance from the coil, 
which will leave the contact points, or more proper- 
ly speaking, the armature about ^g-inch from the 
core, then by means of the adjusting screw the 
distance can be increased or decreased as desired. 
In placing the vibrating springs and the adjusting 
screw standard, they must be perfectly insulated 
from one another. A piece of mica about 3^ -inch 
thick is interposed between the standard and the 
spring, and the spring having a large Jiole drilled 
in it so as to clear the screw that fastens all down 
together on the board. The next consideration is 
the core for the induction coil. It can be made of 
one solid piece of soft iron if desired, but the writer 
prefers to make it from a bundle of soft iron wires 
all being soldered together as shown in Fig. 6. An 
easy way to construct this is to get a piece of brass 
tube about 2 inches in length which has a hole in 
it a shade smaller than the hole in the spool of the 
coil. Now cut up all the wires of a length — ^-in. 
wire is a good size — and have them free from dirt 
and grease. Place the tube on end on a flat slab 
of any kind and proceed to fill it up as full of the 
wire as possible. Having melted some solder in a 
ladle for soldering the ends of the wires, fasten 
them all together at the end protruding out of the 
tube by binding a wire around them about J^-in. 



196 



ELECTRICITY AND ITS 



from the end and then dip them in the melted 
solder up to the binding wire. Push the wire 
through the tube till they protrude out as much as 
they did on the other end and repeat the ope- ation. 
T tfow the wires are permanently fastened together 
in one bundle and the binding wires can be re- 
moved. Turn up a neat knob of hard wood or 
hard rubber, as preferred, and drill a clearance 




Figure 7, A. 

hole about ^-in. through the centre, next drill and 
' tap a hole ^-in. in the centre of the core and fasten 
the knob on and the core is complete. To fasten 
the coil to the board, cut a groove in it of about 
ys-in. deep and to conform to the diameter of the 
spool ends. Cut two strips of ^-in. brass the same 
width as the spool ends arc thick, bend and drill as 



RECENT APPLICATIONS. 



19^ 




198 ELECTRICITY AND ITS 

shown in Fig. 7, B while the same view shows them 
attached. Make the handles, from which the shock 
is taken, of brass tube about ^ -in. outside diame- 
ter and about 3 \-in. thick, turn two small discs ^-in. 
thick and drive them, one in each end of each tube 
and solder them. To these ends fasten wires 
about 3-ft. long, clear the insulation of the othei 
end and fasten in the binding posts that are in con- 
tact with the secondary coil, and now with the aa~ 
dition of a battery the instrument is complete. 

By polishing all the brass work and making the 
knob on the end of the core of hard rubber, the 
instrument will present a very neat and attractive 
appearance. Several other points of embellish- 
ment might be added which the writer will leave 
for the amateurs fancy to dictate. 



KECENT APPLICATIONS. 



im 



CHAPTER XI. 

THE INCANDESCENT LAMP. 

The incandescent lamp has become familiar tc 
almost everyone who lives in a large city. We see 
it in practical use in most public buildings and in 




THOMSON-HOUSTON LAMP. 



many private dwellings. It is also used extensively 
to furnish light in our factories and to replace our 
old fashioned street gas-lights. Considering the 



200 



ELECTRICITY AND ITS 



short time (which is about ten years) since the 
incandescent lamp was invented, it has made rapid 
strides toward perfection. 

On page 199 will be found an illustration of an 
incandescent lamp, such as is used for all ordinary 
purposes at the present time. 




The lamp consists of a glass globe or bulb, 
from which the air has been exhausted, con- 
taining a carbonized fiber of bamboo. This carbon- 
ized fiber is attached to two platinum wires fused 
in the glass, the free ends of the wires being 
connected to the copper sockets of the lamp, which 



EECEXT APPLICATIONS. 201 

are insulated from each other by Plaster of Paris. 
The wires are then connected to the external 
circuit. Fig. I is a sectional view of a familiar type 
of the 1 6 candle-power lamp, c being the carbon 
loop ; b the glass bulb ; / the collar ; and w w the 
platinum leading wires. In order to produce light 
the carbon loop is brought to a white heat or 
incandescence, by the heat energy of an electric 
current. No known substance will endure this 
temperature of white heat without, in time, dis- 
integrating, but carbon seems to stand this white 
heat longer than any other substance especially 
when it is enclosed in a high vacuum. But all 
incandescent lamps "fail" after running a certain 
number of hours, because their filaments disinte- 
grate—they do not burn at the temperature of 
incandescence. The average life of an incandes- 
cent lamp is from six hundred to one thousand 
hours, after that the filament becomes worthless 
and must be renewed. 

The carbon loop is usually made from some 
vegetable fiber, such as is obtained from bamboo 
or some plant possessing a similar structure. Silk 
is used by some manufacturers but as yet has not 
proved to give as good results as bamboo. As the 
object is to obtain a compact carbon, a fiber rich 
in this element is the best. It must have a straight 
grain and possess great tensile strength in order 
to endure the process of reducing its size to the 



202 ELECTKICITY AND ITS 

required proportions. This process consists of 
shaving or drawing it through a series of dies, 
each die removing a small portion of the surface 
until the proper diameter is obtained. This diame- 
ter is varied according to the candle-power and 
voltage of the lamp. Having brought the fiber 
to the proper size, they it isbaked or carbon- 
ized by a method similar to gas making, except 
that the residue is the article particularly desired, 
and not the gases that are driven off. The fiber is 
now bent around a graphite block so as to form a 
loop, a number of fibers being put on each- block, 
which are then packed in a pot containing carbon 
dust and subject to the intense heat of a furnace 
for a number of hours. 

During this process air must be excluded from 
the pot containing the fibers, otherwise a certain 
portion of their structure will be burned. Having 
properly carbonized the fiber it is attached to the 
wires (w w Fig. I,) which have previously been 
fused into the glass (s); this is now enclosed in the 
glass bulb and the lamp is now ready to be connected 
to the mercurial vacuum pump by means of which 
the bulb is exhausted of air; Fig. 2 shows the Geissler 
Pump used for this purpose. B I and B 2 may be 
called the mercurial bulbs or reservoirs which are 
connected by a U shaped bulb, by means of which 
the mercury is made to flow from one bulb to the 
other, thereby alternately emptying and filling 



RECENT APPLICATIONS. 



203 



each bulb ; / and i are the stop cocks, v is the 
valve opening upward, c is the valve opening down- 
ward, d is a reservoir containing substance for 
absorbing any moisture that may be contained in 




the pumps ;._/// are the points where the bulbs 
are sealed when the lamps are detached from the 
vacuum pump. In this pump the mercury is 
forced by the pressure of air from the bulb B i to 



204 



ELECTRICITY AND ITS 



the bulb B 2, driving out the air at the point p. 
The stop cock / is then closed and the vacuum 
pump draws the air out of the bulb B i, causing 




the mercury to fall from the bulb B 2 into the bulb 
B 1. The air in the lamps then distributes itself 
through the tubes into the bulb B 2 and is again 
forced out in the manner described, and so on 



RECENT APPLICATIONS. 205 

until a nearly perfect vacuum is obtained in the 
lamps. Fig. 3 shows the Spreugel type of mercu- 
rial vacuum pump. 

In this system the mercury is made to fall from 
the tube j in a very fine stream in the form of 
small globules, thereby entangling the air in the 
globules and carrying it off into the reservoir r. 

One of the most recent improved methods of 
obtaining a high vacuum for incandescent lamps is 
by the Packard Vacuum Pump and the following 
description and illustrations were kindly furnished 
for this book by the Electrical Engineer of New 
York. 

While the mercury pump leaves nothing to be 
desired as a method of obtaining a high vacuum, 
its employment in completely exhausting vacuum 
lamps is tedious and expensive. In order, there- 
fore, to expedite and cheapen this important part 
of lamp manufacture, mechanical vacuum pumps 
are now extensively employed to remove the larger 
part of the air contained in the lamps, leaving the 
mercury pumps to complete the vacuum required. 
Probably the most extensively used vacuum pump 
for this class of work is the Packard Vacuum Pump, 
built by Mr. Norman Hubbard, of 93 Pearl Street, 
Brooklyn, N. Y. Our engraving, Fig. 4 shows 
the No. 4 pump, and as will be seen, the cylinders 
are placed vertically in a cast-iron box which serves 
as a bed plate and water jacket, and on which the 



206 



ELECTRICITY AND ITS 



frame and working parts are mounted. Each cylin- 
der is entirely independent of the others and can 
be used separately or connected up as required. 




FIG. 4. — THE PACKARD VACUUM PUMP FOR EXHAUSTING 
INCANDESCENT LAMPS. 

The suction pipes are connected at the bottom of 
the jacket by means of ground unions which are 



PECENT APPLICATIONS. 



207 



provided with traps to arrest any mercury or dirt, 
and the exhausts are piped to a pot which acts as 
a trap to catch the oil used in lubricating the cylin- 
ders, which is saved and may be used over again. 
No water is used in the cylinders. 




FIG. 5 — THE PACKARD VACUUM PUMP FOR EXHAUSTING 
INCANDESCENT LAMPS. 

The valve motion is on the principle of the well- 
known Ritchie valve gear, but containing none of 
its complication. All the valves are opened and 
closed automatically, not requiring an air pressure 
below them to do this work. The main valve stem 
does not pass through the piston head. The clear- 
ance in the cylinders is reduced to a minimum, 
being generally less than * B of an inch, and no 
liquid is used other than sufficient oil to insure 
proper lubrication. 



208 ELECTRICITY AND ITS 

The valves in the piston head have their seats 
close to the bottom, and are entirely enclosed in 
the body of the piston, rendering impossible the 
breakage or giving out of the valve. The exhaust 
valves are contained in a separate bonnet bolted to 
the cylinder head. This bonnet has a screwed 
cover, by removing which the valves can be lifted 
out. 

The company claim that (the barometer being 
at 30 inches) a vacuum exceeding 29^ inches is 
easily obtained. 

The Packard pumps are built in a variety of sizes, 
the smaller ones being designed for the prelimi- 
nary exhaustion of the lamps. The larger sizes are 
designed for the operation of the ordinary auto- 
matic Geissler pumps, where the mercury is raised 
and lowered by alternately admitting the atmos- 
pheric pressure and producing a vacuum above the 
mercury in the lower bulb. The method of con- 
nection of the Packard pump with the mercury 
pump is shown in Fig. 5. 



RECENT APPLICATIONS. 209 



CHAPTER XII. 

ELECTRICAL MINING APPARATUS. 

The field that electricity is destined to achieve 
great industrial victories is in the mines of the 
world. Here, it is now being used for profitable 
service under conditions where heretofore no agency 
could find place for action. Rich deposits of metal 
or mineral, inaccessible to development from the 
difficulty of access, the absence of fuel, or the ex- 
cessive cost of the same, are now capable of a 
profitable working ; and are being rapidly occupied. 
Natural energy in the myriad water powers of the 
country, that for ages have run to waste, often in 
localities where they could not be utilized, now 
take up their yoke of submission, and one to twenty 
miles away from the falls, give ample, reliable, 
economical service for mill and mine. In the pages 
that follow, will be shown some of the applications 
of electrical energy for mining uses, and its adap- 
tation to every class of mining work. 

Nature has generally interposed very serious 
obstacles in all mining operations. In many rich 
mining localities fuel is scarce and transportation 
very high, so that the use of steam power is unprofit- 

14 



210 ELECTRICITY AND ITS 

able. If water power is in the vicinity, intervening 
mountains or other obstacles are often in the way, 
and expensive canals, tunneling or insurmountable 
grades prevent its transmission. In the past the 
lack of a practical and economical method for long 
distance transmission of power, ensuring efficiency 
and commercial success, has led to the abandon- 
ment of many mines of great promise, especially 
2n the West and South. Of course the difficulties 
of all the systems of power transmission increase 
rapidly with the distance, and in mining es- 
pecially — from the nature of the work — distance 
from the source of power is an ever-increasing fac- 
tor. Of the five prominent systems of importance, 
suitable for long distance transmission, namely : 
hydraulic, pneumatic, steam wire rope and electric, 
the latter is the only one that at the distance of 
a thousand feet, or further increase of the same, 
can, in any degree, economically meet the emer- 
gency. Electric transmission of Power means an 
air line from point to point. There are but few 
places where water levels can be run over light 
grades and in a direct course. In the majority of 
cases canal courses are circuitous and grades diffi- 
cult and expensive in the construction. So that 
compared even with the cheapest methods of water 
or wire rope transmission, the direct wire system of 
electric transmission of power has immense econo- 
mical advantages, to say nothing of the great 



RECENT APPLICATIONS. 211 

superiority in its delivery and application to the 
mining work at the mine or mill. Any reliable 
constant water power, with the usual obstacles in 
mining districts, can better, by a very large per- 
centage, be electrically transmitted than by any 
other method whatever. For at least twenty miles 
distance it is possible to transmit electrical energy, 
and distribute the same successfully in detail under 
the most difficult conditions, and for the most pro- 
tracted and exacting service. 

Edison Electric Mining Hoist, — On page 212 
is a view of the Edison Electric Mining Hoist. 
The general arrangement of the two different parts 
can be understood very easily from the view given. 
Direct gearing between the armature and drum is 
used, and all gears are boxed in iron cases to pro- 
tect them from dust or stray stones. At the same 
time the cases can be quickly removed if occasion 
should require to reach the working parts. Every 
part of the machine is designed to give the greatest 
power with the least weight, and by this means the 
machine is made quite light and can be easily trans- 
ported from one part of the mine premises to another. 

The qualities of durability, compactness, ease of 
operation and minimum of wear, so essential in 
mining work, have been carefully attended to in this 
machine. The view presented shows that no extra 
room is taken up by any part of the apparatus. 
Everything is arranged to fit closely upon the base 



212 



ELECTRICITY AND ITS 




llilli 



¥ 



i!l j .K 



RECENT APPLICATIONS. 213 

frame of the hoist. The speed of the motor is con- 
trolled by a switch at one side, by means of which 
the motor can be made to vary its speed by a single 
movement of the switch handle. Turning the han- 
dle to one division will make the motor run slowly, 
through two divisions, faster, and full number of 
divisions, at full speed, w r hile turning the handle in 
the opposite direction, will give similar rates of 
speed with opposite direction of motion. This elec- 
tric hoist is supplying a long felt want in mining 
and mill work, where a convenient and portable hoist 
which can be operated from a lighting circuit already 
installed, has been needed. 

Rotary Diamond Drill- — In all mining machinery 
with the exception of the rock drill, applications of 
the Edison motors are made by gear or pulley. 
They now have ready for the market a rotary dia- 
mond drill, which has shown very good results in 
experimental work, and will soon be applied to 
regular mining work in several leading mines. A 
good electric rotary mining drill has been the miss- 
ing link in electric applications for mining work. 
This one is light, compact, simple and easy to 
operate. The motor is completely encased, so that 
it is impossible for dust, dirt or stray stones, to 
lodge in the working parts. The whole drill is 
mounted on an adjustable frame so that it can be 
very easily set in any position desired, or set at 
work at any part of the mine. 



*«14 



ELECTRICITY AND ITS 




ROTARY DIAMOND DRILL. 



RECEXT APPLICATIONS. . 215 

The current for operating the drill is supplied 
at a constant voltage or potential ; the number of 
volts depending on the potential used for trans- 
mitting power throughout the mine. If lamps are 
needed, they can be supplied with current from the 
same main current wires which supply current to the 
drill, and when in such use are connected in mul- 
tiple arc across the main wires. 

Edison Locomotive for Metal Mines. — It has 
not been so difficult a problem to adapt electric 
motor service in the tramways of coal mines as in 
those of metal mining, where great compactness, 
strength and traction for the space that can be occu- 
pied are required. To get the needed energy into the 
required limited space has been the most difficult 
problem of solution. In the Edison locomotive 
for metal mines it is claimed that these necessary 
conditions have been secured. The outside dimen- 
sions of a 15 H. P. locomotive for an 18 inch gauge 
are 30 inches in width, 30 inches in height, 62 
inches in length. We illustrate the locomotive 
which shows a machine of a total weight of from 
3,000 to 4,000 pounds. Such machines can be used 
in a space where even a mule could not be worked. 
This electric locomotive is simple, powerful and 
compact, and is built with special reference to the 
arduous duties required of such a machine. The 
gauge is 18 inches, but it can be accommodated to 
any gauge used in ordinary mining work. In order 



2ie 



ELECTRICITY AND ITS 




< 

H 

2* 



ft 

N 

> 

H 




u 



RECENT APPLICATIONS. 217 

to protect the machine from damage, all the work- 
ing parts are completely boxed in, as shown 
in the cut. 

The speed of the motor is under complete con- 
trol by a switch which throws the winding of the 
field into different electrical combinations, thus 
varying the speed of the motor without the use of 
any wasteful resistance. The direction of rotation 
is also governed by the same switch, so that the 
operation of the motor is very simple, and it can 
be put in charge of an ordinary workman. Any 
system of conveying the current from the dynamo 
to the locomotive can be used, either using the 
rails as one side of the circuit for the return of the 
current, or else employing a complete metallic cir- 
cuit by the use of a double overhead trolley wire. 
In these cases, a trolley pole, shown in the view, 
carrying at its upper end trolley wheels for making 
running contact with the overhead wires, is attached 
on the rear of the locomotive car. This mining; 
locomotive is now being manufactured by the 
Edison Electric Railway and Motor Company. 

The Edison Electric Coal Cutter. — The great su- 
periorly of mining coal by machinery instead of hand 
has developed a number of coal cutting machines, 
among others what are known as the " Rotary Coal 
Cutter," "The Reciprocating Coal Cutter," and the 
"Cutter Bar." This new feature in mining ma- 
chinery is of great value to the coal mine industry, 



218 ELECTRICITY AND ITS 

because of its great saving of labor and expense. 
By its use, also, it is possible to have the working 
places more concentrated, and thereby saves a large 
amount of expense in the form of dead work, such 
as keeping open gangways, etc. To get an approx- 
imate idea of the cost of mining coal by machinery 
as compared with hand labor, it can be stated that 
a cutter in the^Hocking Valley is capable of giving 
an output of 80 to 85 tons a day, at a cost of 43 
cents per ton ; the same work done by hand would 
cost 70 cents per ton. 

The Edison General Electric Company have ad- 
ded to their extensive list of mine appliances the 
most approved form of coal cutter, namely, the one 
using the cutter bar— see illustration page 219. This 
machine has a shaft revolving parallel with the coal 
in a horizontal plain, with knives distributing all 
around the surface, so as to cut a groove in the 
coal the entire length of the bar. This machine has 
the advantage of great strength, and excels all 
others of the same class in the matter of design, 
the material being distributed to give the greatest 
possible strength and rigidity. A great feature of 
this machine is that the coal is cut in an upward di- 
rection which greatly assists in keeping the machine 
down to the ground, and avoids the necessity of 
carefully fastening it by means of braces or jacks. 
A draw back which has been experienced in several 
types of coal cutters is that by the arrangement of 



RECENT APPLICATIONS. 



219 




220 



ELECTRICITY AND ITS 



the bearings which hold the cutter bar, the bar has 
to withstand not only the strain due to the resist- 
ance of the coal being cut, but also that which the 
chain itself has to overcome. 

In the Edison Machine a counter shaft is placed 
behind the cutter bar to which the power is trans- 
mitted direct from the motor by means of four 




THOMSON-VAN DEPOELE MINING LOCOMOTIVE. 

chains. The power is then transmitted to the bar 
by means of gears, so protected as to prevent the 
coal dust from settling between them. The ma- 
chine is especially adapted to withstand the rough 
uses to which it is subjected in mines, and it enjoys 
the advantage of simplicity in design, great strength 



RECENT APPLICATIONS. 221 

in the bar actually doing work, and the use of rol- 
lers for the sliding frame which reduces to a mini- 
mum the friction between it and the stationary bed. 

The motor is capable of giving 15 H. P. when 
doing steady work ; when running off and on only 
it is capable of giving a far greater pow r er. The 
motor runs without sparking, and has all of its vital 
parts well protected, the insulation of the machine 
having been given special attention. 

This coal cutter is capable of making a cut of 4 
feet wide, 5 feet 6 inches deep, by 3^ feet high 
and can be operated by two men ; it can be moved 
from place to place, and the great flexibility of the 
of the electric current enables the miner to work 
in places where it has heretofore been impracti- 
cable to transmit other forms of pow r er for the opera- 
tion of these machines. 

The Thomson-Van Depocle Mine Locomotive. — 
The general appearance of the Thomson-Van De- 
poele locomotive is shown in illustration, on page 
220. The No. 4 machine, with a capacity of 60 
horse-power, has a total height from top of rail of 
39 inches. The controlling devices are all at one 
end, and the body of the locomotive being so low 
that the view is unobstructed in either direction, 
the operator need not change his position in re- 
versing the motion of the locomotive. Two Elec 
trie Parabolic Reflectors are provided at each end, 
making the track clearly visible for long distances. 



222 ELECTEICITY AND ITS 

The trolley is of the double-elbow pattern, found so 
admirably suited to mine work in previous installa- 
tions. It accommodates itself to the varying heights 
of the trolley wire within any reasonable range. 
The sheet-iron covering makes a complete water- 
tight armor, protecting the moving parts from 
danger of falling rocks or bodies of ore and coal. 
The illustration shows the locomotive in an en- 
larged chamber, but about to enter a tunnel whose 
height from top of rail is scarcely four feet, hence 
the depression of the trolley wire as shown. 

Many other electrical machines have been invent- 
ed for mining purposes, but the space allotted for 
this chapter will not permit the author to describe 
them; so let us proceed to the next subject. 



RECENT APPLICATIONS. 223 



CHAPTER XIII. 

THE MODERN ELECTRIC RAILWAY. 

In 1879 Dr- Siemens constructed and exhibited 
at Berlin the first Electric Railway. Previous 
experiments had been tried by him in 1867, but 
without success. 

In 1880 Stephen D. Field filed papers at the 
Patent Office in Washington, D. C, for a patent 
on the Application of the Electric Motor to the 
Street Railway. Papers were also filed the same 
year by Dr. Werner Siemens and Thomas A. 
Edison. The first Electric Railroad put into 
operation in the United States was constructed 
and exhibited by Thomas A. Edison at Memo 
Park, N. J., in 1880. The Chicago Electric Rail- 
way was the first constructed in this country for 
business purposes and was considered at that time 
a success. This was operated by the Van Depoele 
system. But all this was a beginning, and not till 
1886, when the Sprague System was established 
by the construction of the Richmond Passenger 
Railway at Richmond, Va., and put into operation 
in 1887, can it be said that we had a modern elec- 
tric railway. This was followed by the construction 



224 ELECTRICITY AND ITS 

of the first Thomson-Houston Electric Railroad at 
Crescent Beach, Mass., July ist, 1888. 

That the Electric Railroad is a success and that 
it has come to stay no one can have a doubt. Of 
the future developments, well, who can tell ? No 
doubt but electricity is in its infancy and that 
within a few years it will make still greater strides, 
that we may yet not only see the street cars run 
by electricity, but also the steam railway, which 
means no smoke, no cinders and faster travel. 

There are two principal systems of Electric 
Railways at present ; the overhead system and the 
storage battery system. In the former system, as 
in the Edison and Thomson-Houston, the cars are 
equipped with motors and the current taken from 
the overhead wire by means of a small structure on 
top of the car. This consists of a light trolley 
pole, supported upon a stout spring, so that it may 
move in any direction, and having at its upper 
end a grooved metal wheel, making a running 
flexible contact on the under-side of the working 
conductor. The flexibility of this arrangement is 
very great, it being able to follow with facility 
variations of the trolley-wire four or five feet in 
either a horizontal direction, or more than twelve 
feet in a vertical direction. By this means a con- 
stant contact is made by the trolley-wheel at 
different rates of speed or around curves, and for 
different heights of the trolley-wire. The current 



RECENT APPLICATIONS. 225 

taken from trolley-wire passes through the motor, 
through the wheels of the car to track, back to the 
dynamo. The rails being grounded and usually 
connected to a continuous conductor running the 
whole length of the line. See Fig. i. 

In order to secure the necessary track adhesion 
by means of independent driving, and to permit 
the entire weight of the car and its contents to be 
available for traction, two motors are generally 
used on each car, one for each axle, with indepen- 
dent driving ; at the same time both motors are 
capable of perfectly simultaneous control by a 
switch placed at either end of the car. This switch 
controls both the speed and the direction of move- 
ment of the motors. These Motors are of jy^, or 
15 horse-pow r er normal capacity each, making an 
aggregate of 15 or 30 horse-power on each car. 

In the Thomson-Houston system the regulation 
of speed and current is governed by a Rheostat, 
which is an apparatus made up of mica and sheet 
iron, and is used to throw a variable resistance into 
a circuit at will. 

In the construction of the electric motor for 
car propulsion the motor acts simply for the trans- 
formation of electrical energy with mechanical 
energy. A current of electricity is sent through 
the armature and fields of the motor, which causes 
the armature to revolve. 

Another, and by no means the least part of the 

15 



226 



ELECTRICITY AND ITS 




\ 



\ 




RECENT APPLICATIONS. 227 

electric railway is the power station, which con- 
tains the boilers, steam engines and electrical 
apparatuses. Engines are now made especially to 
drive dynamos, as it requires a uniform speed to 
obtain good results from a dynamo. 

The electrical apparatus consists of dynamos for 
generating the current, switch-boards, armatures 
and volt -meters. The feeder, or connection board, 
interposed with fuses, which melt and break the 
current if it exceeds a certain amount ; an auto- 
matic circuit breaker ; also an apparatus known as 
a lightning arrester, used in case the cars or line 
are struck by lightning. 

There is at present two classes of electric rail- 
way motors, fast speed and slow speed. With the 
fast-speed motor the armature revolves with great 
rapidity, and the motion is communicated to the 
axle of the car by means of gears and pinions. 
In the slow-speed motors the intermediate gears 
and pinions are left out, there being only one gear 
and pinion, the gear being on the axle of the car 
and the pinion on the shaft of the motor. At 
present, electricians are working to obtain a gear- 
less motor whereby the motion may be communi- 
cated directly from the armature shalt to the axle 
of the car. 

The General Electric Co.'sjf^ Raihvay Motor. — 
The rapid growth of passenger traffic resulting in 



228 



ELECTRICITY AXD ITS 




RECENT APPLICATIONS. 229 

the increasing use of heavy cars on the lines of 
many of the electric roads operating within city 
limits has induced the General Electric Company 
to design and manufacture a motor known as the 
GE-54. 

It is adapted for use on a minimum gauge of 
48!" and in general design and construction is 
similar to the GE-52. 

Rating. — On 500 volt circuits the GE-54 
railway motor with three-turn armature will de- 
velop 25 H.P. The output is based on the 
standard rating ; that is, a maximum rise of 75 ° C. 
in the temperature of this winding after a run of 
one hour at full rated load, the temperature of 
the surrounding air not exceeding 25 ° G 

Magnet Frame. — The magnet frame is in the 
form of a hexagon with well rounded corners, and 
is cast in two pieces of soft steel of high mag- 
netic permeability. The two castings are bolted 
together, but the front bolts are hinged in order 
that the lower frame may be swung down con- 
veniently so as to permit inspection or repairs of 
the field or armature. 

There is an opening in the frame just over the 
commutator large enough to provide for the re- 
moval of the brush holders and brush-holder yoke 
and also to permit of inspection of the commutator 
and brush holders. The cover, which is of 



230 ELECTRICITY AND ITS 

malleable iron, is held in place by an adjustable 
cam locking device, and can be readily removed 
when necessary. The lower frame has a small 
opening directly under the commutator, also pro- 
tected by a suitable cover. 

Bearings. — The armature and axle bearings 
consist of cast-iron shells of ample thickness to 
insure stiffness, and are lined with Babbitt metal 
swaged into the shells so as to make them com- 
pact and tight. 

The bearings are designed for the use of both 
oil and grease. The oil is fed to the shaft from 
oil wells in the caps by means of felt wicks, while 
the grease reaches the bearing from the grease 
box which is over each bearing, through a slotted 
opening in the top of the lining. 

The armature bearings, which are built on the 
outboard principle, are 7i"x 2 fat the pinion end 
and 6" x 2\" at the commutator end. The sup- 
ports for the upper parts of the linings are cast as 
parts of the upper half of the magnet frame, and 
a large recess is cored between the inner end 
of the lining and the frame to accommodate the 
combined thrust collar and oil guard. The design 
of the oil guard practically prevents oil or grease 
from working into the motor frame. The lower 
half of the armature bearing is supported by a cap 
bolted to the upper frame, and an opening is pro- 



RECENT APPLICATIONS. 231 

vided to allow free egress of the lubricant after it 
has passed through the bearing. 

The axle-bearing caps are bolted to the under side 
of extension pieces, which are cast on each end of 
the upper half of the magnet frame, and which 
reach over and partly enclose the car axle. These 
parts are bored out to support and enclose the 
axle linings, which are 8" long. 

Pole Pieces and Field Coils. — The pole pieces 
are built up from thin soft iron laminations, riveted 
together, and bolted to the frame by through bolts 
with nuts on the outside. 

The four field coils are placed at an angle of 
45 from the horizontal, and are held in place by 
pressed steel flanges or spool holders which are 
clamped to the pole pieces. The coils are made 
of asbestos, cotton covered wire, and are further 
insulated with wrappings of varnished cloth and 
tape. The insulation on the coils is subjected to 
a high potential test of 4000 volts alternating cur- 
rent. 

Armature. — The armature is of the ironclad 
type, and the core is built up of thin soft iron 
laminations which are carefully japanned and 
securely keyed to the shaft. The laminations are 
clamped at each end by cast-iron heads which are 
also keyed to the shaft. The core is hollow and 
is ventilated by the air which enters the pinion 



232 ELECTRICITY AND ITS 

end of the core, and passes out through the air 
ducts placed at regular intervals among the lam- 
inations. 

The armature winding is of the series drum 
type, the number of turns per coil varying with 
the requirements of each case. The coils are made 
up in sets ; and, before being placed in the slots 
of the armature core, each set is formed, and 
thoroughly insulated with specially prepared tape 
and cloth which have high insulating qualities and 
are practically impervious to moisture. 

The terminals of each coil are brought directly 
to the commutator segments, and soldered so as to 
properly connect the coils to each other and at the 
same time form the connections between the 
windings and the commutator. They are so ar- 
ranged that any coil or number of coils can be 
easily removed and repaired, or replaced with new 
coils when necessary. The coils are held in place 
in the slots and on the ends of the core by bands 
of tinned steel wire held together by clips and 
soldered. The end windings are thoroughly 
protected by canvas, and at the pinion end they 
are further shielded by a flange which extends 
past the windings and prevents injury from care- 
less handling. 

When the coils have been placed on the core 
and the armature is completed, the insulation 



RECENT APPLICATIONS. 233 

between the winding and the core is subjected to 
a high potential test of 2500 volts alternating cur- 
rent. 

Commutator. — The commutator consists of 115 
hard-drawn copper segments which are slotted at 
the back to receive the armatures wires, insulated 
with carefully selected mica, and securely clamped 
to a malleable iron shell. The diameter of the com- 
mutator is 82", and the wearing length 3 J" \ with 
a depth of 1 ~' measured at the front end. The 
cone clamping insulations are of the best quality of 
mica, built up and pressed hard and compact. The 
mica between the segments is of a softer quality, 
which insures even wear of segments and mica. 

After the commutator is completed, the insulation 
between the segments and the shell is subjected 
to a high potential test of 4000 volts, and that 
between adjacent segments, to 400 volts alternat- 
ing current. 

Brush Holders. — The two brush holders are of 
cast brass, and are clamped to a hardwood yoke 
which is bolted to the top of the magnet frame, and 
can be removed through the opening in the frame 
over the commutator. The brushes slide in finished 
ways, and are pressed against the commutator by 
pressure fingers, which give a practically uniform 
pressure throughout the working range of the 
brushes. 



RECENT APPLICATIONS. 235 

All leads from the motor to the cable are 
brought out at the front of the motor through 
rubber bushed holes in the magnet frame. 

Gearing. — The pinion is of steel, and is bored 
to a taper fit on the shaft. The gear also is of 
steel, and gear and pinion have a 4i" face and No. 
3 pitch. They are protected by a dust-proof case 
of malleable iron which is securely bolted to the 
upper half of the magnet frame. 

Suspension. — The GE-54 motor is adapted 
for use with either nose or yoke suspension. Four 
bolts are provided at the front of the motor for 
attaching the suspension bar, 

When the motor is mounted on 33 wheels, the 
clearance between the bottom of the motor and 
the top of the rails is 5 J" and that between the 
bottom of the gear case and the top of rails, with 
the maximum gear reduction is 4§". 

A Trolley Man-of- War. — The accompanying 
illustration shows a trolley man-of-war, built in the 
shops of the Fitchburg & Leominster Street Rail- 
way Company, at Fitchburg, Mass. This pioneer 
of all land craft is not to be despised when it comes 
to a question of force. Dainty " barkers" peep 
out through her port-holes, prototypes of the smil- 
ing faces that gleam from the sides of the flagship 
New York. This trolley man-of-war, or white 
cruiser on wheels, has been dignified with the 



236 



ELECTRICITY AND ITS 



-j_>JLi— ». 




A TROLLEY MAN-OF-WAR. 



RECENT APPLICATIONS. 237 

name of President-elect William McKinley. While 
her mission is that of protection, so far, she is quite 
likely to be utilized for that purpose in the days 
that are to come. 

The McKinley is designed to run on electric 
roads of standard gauge, and it is very likely that 
the queer craft will have many imitations before 
long. She is in appearance a miniature, to a great 
extent, of the big cruisers that have followed 
Admiral Bunce's flag for so many months. Her 
superstructure is painted green, her hull and spon- 
sons white, her guns and ironwork black. She 
carries ioo men, officers and crew; and is 37 feet 
long, 9 feet wide, 12 feet high. The lines on 
which she w r as constructed were taken from the 
model of the battle-ship " Brooklyn," by Naval 
Architect Henry P. Lapointe. 

Originally the McKinley was a flat car ; and she 
was extended fore and aft, so that finally her length 
from stem to stern was 37 feet. She has a double 
row of port -holes on each side ; and as she ad- 
vances toward you, you see the sullen countenance 
of two grim six-pounders, while peeping from the 
tiny turret on the gun-deck is a ferocious-looking 
18-pounder. The craft is equipped with two 30- 
horse-power motors. 

The builder believes that the McKinley demon- 
strates the fact that it is possible to construct a 



288 ELECTRICITY AND ITS 

car for operation on street railroads in cities that 
would be of infinite use in case of riot. It is not 
beyond the range of the ability of modern me- 
chanics to build a car that would be bullet-proof, 
and really constitute a travelling fort. Such a car 
might carry several pieces of artillery, or to be 
equipped with the light guns that are used in the 
navy, the recoil of which would not be sufficient 
to damage the fort on wheels in any way. 

Indeed, it is believed that a car constructed on 
the same model as the McKinley, only, of course, 
of substantial material, would form a very effective 
protection for a company of men whom it was 
necessary to move from one part of the city to 
another. Certainly it would be very much easier 
to transport guns and men in this fashion, in case 
of riot, than in the ordinary way ; and it is also 
true that movements could be made from one 
point to another with far greater celerity. — Elec. 
Review. 

The Storage Battery Car System. — In this sys- 
tem the power is furnished by storage-battery cells 
or accumulators. These cells are stored when in 
use under the seats of the cars. The batteries, 
when fully charged, are capable of propelling an 
ordinary carload of fifty passengers, over a level 
road, at the rate of nine or ten miles an hour, for 
about six hours, allowing for the average car-stops 



RECENT APPLICATIONS. 239 

and lay-offs at the terminals. The car would, 
therefore, require one change of batteries for a 
day's run of twelve hours. The weight of a 16- 
foot car, equipped with two motors, is about 3 J 
tons, without passengers. The batteries supply 
electric light for inside lamps and head-lights, and 
power for signal bells and alarm gongs. 

An accumulator car can ascend steeper grades, 
and go at a faster rate of speed, either on grades 
or on a level road, than is possible with horses ; 
but always, of course, with a correspondingly 
greater expenditure of energy. In cases of a sin- 
gle excessive grade on an otherwise level road, it 
may be advisable, on the score of economy, not to 
provide power for each car sufficient for surmount- 
ing such grade, but to use an auxiliary motor car, 
or tow-horse, as is now customary. 



240 ELECTRICITY AND ITS 



CHAPTER XIV. 

WIRELESS TELEGRAPHY. 

The wireless telegraphy apparatus is operated by 
the effect of Hertzian waves. The waves were 
named from Dr. Hertz, who devoted a great deal 
of time to the elucidation of their properties. The 
waves vibrate at the rate of about two hundred 
and thirty millions per second. They are longer 
than light waves, but do not undulate so rapidly 
as those of heat. They may be produced by a 
sudden discharge of electricity from an induction 
coil, Ley den jar, Wimshurst Machine, a flash of 
lightning, etc. In order that we may see their 
effect they must be received with some sort of 
apparatus capable of the same rate of vibration, or 
in time with them. This apparatus is called the 
Coherer. Messages can be sent much farther 
over water than land by wireless telegraphy, — from 
150 to 200 miles. 

The Marconi system seems to be the best at 
present, and we will give a brief description of the 
apparatus. 

The Coherer. — If a glass tube containing iron 
filings, and furnished with projecting wings or 



RECENT APPLICATION-. 241 

wires, be placed in the path of Hertzian waves, the 
filings will assume a symmetrical position. The 
coherence is quite strong, and the resistance of 
the filings to a passage of current of electricity is 
lowered. This is the principle of the coherer. 
Now, if a battery is connected in series with the 
glass-tube (or coherer) and with an electric bell, 
sounder, or other apparatus, the ordinary resistance 
of the filings may be so great as to prevent suffi- 
cient current from passing through the coherer to 
produce any visible effect. But immediately on 
receiving the force of the Hertzian waves, the 
filings cohere, and so lower the resistance that the 
current passes freely, and causes the apparatus to 
work. 

In all wireless telegraphy experiments a system 
of -" tuning" must be employed in order to estab- 
lish perfect unison between the transmitter and 
receiving apparatus. This tuning is very essential 
to the privacy of the message. The transmitter 
and receiver are so tuned, or syntonized, to each 
other that no message can be " tapped " or re- 
ceived except by the instrument for which it is 
intended. The Marconi receiving apparatus has 
two wings, or " capacities," which are used not 
only as conductors of Hertzian waves to the co- 
herer, but as tuning accessories ; without these the 
receiver would not respond so rapidly or accurately. 



242 ELECTKICITY AND ITS 

The Receiver. — A simple receiver can be made 
by using a common telegraph sounder or even an 
electric bell. In the path between the sounder 
(or bell) and the battery place the coherer. The 
coherer in its ordinary state presents so much 
resistance to the battery current that sounder or 
bell will not work. But if the coherer is put in 
tune with the transmitter, which is to emit the 
Hertzian waves when a spark passes between the 
electrodes of the transmitter, the waves set up by 
it will break down the resistance of the coherer, 
and cause the battery current to pass, and operate 
tire sounder or bell. 

A difficulty to overcome is, unless some means 
be employed to restore the particles in the 
coherer to their original non-conducting state, 
the current from the battery will continue to 
flow through the sounder or bell. We must 
decohere the filings. For this purpose we have 
a little rod and hammer arranged in such a 
manner that when the sounder or bell works it 
taps against the glass of the coherer, and ef- 
fects the decoherence of the filings. A diagram 
of the Marconi original apparatus is given on 
page 243. By referring to the diagram you 
will become familiar with the parts and under- 
stand its operation. 



RECENT APPLICATIONS. 



243 




TRANSMITTER. 



RECEIVER. 



Transmitter. 

A is the contact breaker. 

B is the tube of vaseline oil in which the large 
brass balls are half immersed. 

4-4 are the two small brass balls. 
C is the induction coil. 
D is the battery. 



Receiver. 



E is the coherer. 
F\s the decoherer. 



244 ELECTRICITY AND ITS 

G is the telegraph sounder. 
H is the battery which operates the sounder. 
/ is the battery which operates the decoherer. 
J J are the resonators. 

The coherer is also connected to the earth and 
to the sky pole. This pole varies in height, depend- 
ing upon the distance that a message is to be sent, 
anywhere from ioo to 350 feet. 

In large wireless telegraphy, stations eighteen 
or twenty poles are arranged in a circle. Around 
the tops of the poles is stretched a wire screen, 
thoroughly insulated from the poles which receive 
the Hertzian waves from the transmitter at the 
sending station. Marconi has just succeeded in 
establishing wireless telegraphy signals between 
Cornwall, England, and the coast of New Found- 
land, a distance of over 1 800 miles. 



RECENT APPLICATIONS. 245 



CHAPTER XV. 

X-RAYS. 

The Rontgen or X-Rays were discovered by 
Professor Wilhelm Conrad Rontgen. One of the 
latest theories of these rays is that they emanate 
from the surface or surfaces that are first impinged 
upon by the cathode rays which proceed from the 
negative electrode of the Crookes tube. 

The generating surface is often the anode. 
They are generated by a bombardment of cathode 
rays against a glass of metallic surface. The 
metallic surface seems to be the most powerful 
source, and platinum the best of metals. Hence 
the use of reflectors in Crookes tubes. 

Prof. Crookes was the inventor of this tube, 
hence the name. They are made in various 
shapes. 

Figs, i & 2 show two forms of Crookes tubes. 

The Crookes tube is a necessary adjunct to the 
production of X-Rays. It consists of a thin glass 
globe or bulb into which is fused through the glass 
two platinum electrodes, one for the anode and one 
for the cathode. The anode is the point where the 
current enters the tube. The cathode is the point 



246 ELECTRICITY AND ITS 

where the current leaves. Hence, either electrode 
of the tube may be made the cathode by simply 
reversing the direction of the current. A good 
tube not more than two inches in diameter, and 
with the electrodes inside not over an inch apart, 
with a coil giving a spark one and one-half inches, 
will make fairly good shadow pictures, if the expo- 
sure is long enough. If a larger tube is used the 




FIGURE I. 



coil should give a spark from three to ten inches. 
By this we mean that the secondary current 
should jump in the air the distance between the 
electrodes of the coil the above number of inches. 
If there is a blue glow that shows in a tube, it will 
not produce X-Rays. What light there is to be 
seen should be a green color. The glass bulb is 
exhausted of nearly all air and gases, making 



RECENT APPLICATIONS. 



217 



nearly a perfect vacuum. This vacuum differs 
from that in an incandescent lamp or a Geissier 
tube, viz. : It is so complete that only about one- 
millionth of the original quantity of atmosphere 
remains in the Crookes tube, while the lamp or 
Geissier tube contains one-thousandth or more. 
When a high potential intermittent or alternating 




FIGURE 2. 



discharge from the induction coil is sent through 
the Crookes tube, there appears in the tube a fluo- 
rescent light of a yellowish green color. These 
rays are particularly strong around the cathode, and 
are called cathode rays. 

Several important facts about the Crookes tube 
will bear mention here. First it must be made of 
the thinnest glass possible, and be sufficiently strong 



248 ELECTRICITY AND ITS 

to stand the pressure of the atmosphere. A tube 
made of thick glass will heat to a high temperature, 
while a tube made of thin glass remains quite cool 
under the influence of the discharge, Thick glass 
is more highly fluorescent, but is greatly inferior to 
thin glass in radiographic power. 

The intensity coil is necessary in the production 
of. the X-Rays, where a battery or a dynamo is 
used to furnish the primary current. It consists 
of two coils, a primary and secondary. To these 
are added, for the purpose of intensifying their 
action, a magnetic core consisting generally of a 
bundle of iron wires. An alternating or pulsating 
current is passed through the primary coil and pro- 
duces (by induction) a current likewise pulsating 
in the secondary coil, although the two coils are 
entirely unconnected. In order to raise the vol- 
tage of the secondary coil, it is made of a finer wire 
than the primary. A diagram of a battery appa- 
ratus for X-Ray work is given, in Fig. 3. 

A is the plate holder with objects lying upon it. 
B is the Crookes tube, C the high potential induc- 
tion coil, D the storage battery, consisting of at 
least 4 cells. 

The object of which you wish to get a shadow 
picture must be placed between the Crookes tube 
and the plate holder. 

By the aid of this new form of radiation we are 



RECENT APPLICATIONS. 



249 



enabled to photograph objects concealed in a box, 
a book, a letter case, etc., and even to lay bare the 
skeleton of a living or dead animal. Its applica- 
tion to surgery will be of great value, as by aid of 
these rays the surgeon may locate the exact posi- 
tion of a tumor, bullet, fracture, etc. Its value to 




FIGURE 3. 



chemistry, metallurgy, and other branches of 
science is at present inestimable. 

The apparatus necessary to produce these rays 
is a Dynamo, Battery, or a Static machine, an In- 
duction Coil and a Crookes tube or its equivalent ; 
for example, an incandescent lamp with its fila- 
ment broken and electrodes properly placed, and 
the bulb exhausted to the proper vacuum. The 



250 



ELECTRICITY AND ITS 



photographic plates used are the ordinary quick dry 
plates. 

Fig. 4 shows X-Ray pictures of the hands of 
two different persons. A is a lead pencil which 




FIGURE 4. 



was lying upon the plate holder. The dark part 
is a metal cap containing the rubber eraser. As 
you will see, the lead shows quite distinctly. 



RECENT APPLICATIONS. 



251 




Various Types of X-Ray Tubes. 



252 ELECTRICITY AND ITS 

The fluoroscope is a device to be used in visual 
examinations of opaque objects by means of 
X-Rays. It consists of a wooden box made light 
tight, and shaped as seen in the engraving. 

On the end to be held before the Crookes tube 
is fastened a sheet of cardboard ; one side is covered 
with a crystalline chemical salts which become 
fluorescent when placed in the path of the X-Rays. 

By placing an opaque body between the tube 
and the cardboard of the fluoroscope a shadow is 
thrown upon it, and is visible to the human eye. 
It was invented by Edison, who discovered that 
platino-cyanide of barium had the property of 
fluorescence, and was the salts originally used. He 
has since substituted the tungstate of calcium, which 
he found has the same properties to a much higher 
degree. The crystals are very minute, and are dis- 
tributed very evenly over the cardboard. 

Any object may be seen instantly by the fluoro- 
scope if the X-Rays are being developed. 



RECENT APPLICATIONS. 253 



CHAPTER XVI. 

THE ELECTRIC FOUNTAIN. 

An electric fountain is a fountain with appa- 
ratus for illumination of its water jets by electric 
light. The colors are changed by sending the 
light through different colored glass plates, and 
various, combinations of colors are obtained which 
make many beautiful effects. A description of the 
Willow Grove Park Electric Fountain will give the 
reader a good idea of the construction. 

The fountain structure measures fifty feet 
across ; and it has two basins, — one five, and the 
other eight feet above the lake. It contains 
thirty-eight nozzles, varying from f to i| inches 
in diameter, and eight hundred and sixty-seven § 
and i inch jets arranged to throw columns and 
sprays of water into the air, permitting a large 
variety of combinations to be made. When these 
are illuminated by the powerful electric lights they 
produce beautiful iridescent effects. The photo- 
graph from which our illustration was reproduced 
was kindly loaned to us by Mr. Darlington. This 
night view of the fountain was taken by a five- 
minute exposure. 



254 



ELECTRICITY AND ITS 




WILLOW GROVE PARK ELECTRIC FOUNTAIN. 



RECENT APPLICATIONS. 255 

The electrical illumination is obtained by power- 
ful electric arc lights beneath the fountain. The 
colors are produced by means of colored screens 
placed between the lamps and the plate-glass 
covered funnels in the ceiling of the fountain 
basement. The colored screens are rotated and 
controlled by means of independent hand wheels 
located at a common point, and varied by an 
operator to produce the desired combination of 
colors. 

The funnels in the roof through which the light 
passes are cast-iron turrets, twenty-two inches in 
diameter and twenty-six inches high, with plate- 
glass tops. There are eight in the lower and 
seven in the upper basin. 

The roof of the basement is eight feet high at 
the sides, and is thirteen feet in the middle. 

The fountain basement is connected with the 
operating rooms on shore by means of a tunnel 
ninety feet long, five feet high, and three and one- 
half feet wide, and has an arched roof. The main 
structure of the fountain is cement-covered brick- 
work, the vases being cast iron, and are painted. 

The pipes running along the bottom of each 
basin are endless, the main feeder and the 
branches to the nozzles and jetted pipes being con- 
nected to the circular pipes by T joints. The 
central nozzle has direct pipes. 



256 ELECTRICITY AND ITS 



CHAPTER XVII. 

ELECTRO-MAGNETIC SURGERY. 

Electricity is now used considerably in sur- 
gery and medicine. The following description of 
removing iron particles from the eye will give the 
reader an idea of one of the principal uses it is put 
to. One useful application of the electro-magnet 
is in locating or extracting particles of iron or steel 
lodged in the eye. The simplicity and utility of 
this plan are obvious, and it is found to be of real 
value to surgeons. The illustration shows the 
apparatus installed in one of the operating rooms 
of the New York Eye and Ear Infirmary, to take 
advantage of the attractive power of the electro- 
magnet. The soft iron core of the large magnet 
here used is about two feet long and three inches 
in diameter, pointed at each end, as shown. The 
winding is disposed on spools in the manner indi- 
cated in the picture, and is supplied with current 
from the house mains. The whole magnet rests 
on a stand, and is arranged to turn easily at the 
touch of a hand. The practical value of the mag- 
netic appliances is described in the Illustrated 



RECENT APPLICATIONS. 257 

American, from which the picture is reproduced 
by George B. Waldron : 

Suppose, as often happens, a worker in iron or 
steel is struck in the eye by a fine splinter of metal 
from a machine. The intense pain which follows 
is as nothing in comparison with the imminent 
danger of losing the eye. The case requires the 
attention of the most skilful specialist. So the 
sufferer is taken at once to the hospital. 

The first thing to do is to locate the piece of 
metal. The instrument used is a small needle 
highly magnetized with electricity. If the splinter 
is on the surface of the eye, it will cling to this 
needle, and can be easily removed. 

But it may have been hurled with such force as 
to have become imbedded in the eye itself. The 
white portion of the eye which surrounds the iris 
or colored ring is composed of tough muscles, 
which can be penetrated with only the greatest 
difficulty. If the iron or steel particle becomes 
imbedded in this muscular tissue, it will not yield 
to the magnetic needle. 

Now comes the use of the large magnet. This 
instrument has a drawing force of 16 pounds. 
As the eye of the patient is pressed toward its 
point the subtle magnetic power begins to draw 
upon the splinter. The metal, struggling for re- 
lease, bulges the eye from the socket. If not too 



258 



ELECTKlCITi: AND ITS 




RECENT APPLICATIONS. 259 

deeply imbedded, the splinter will yield to the 
force, and, leaving the eye, become attached to 
the point of the magnet. 

But, as only too often occurs, the metal may 
strike with such force as to perforate the coating 
and drop down into the cavity of the eyeball. 
Especially is this the case when it passes through 
the iris or the pupil. One instance was mentioned 
by the attendants at the hospital of a splinter 
which passed entirely through the eye, and lodged 
in the coating on the other side of the ball. Ap- 
plied to the eye, the big magnet will reveal with 
accuracy to the skilled sight of the physician the 
position of the troublesome particle. Knowing 
this, he can remove it by an operation. Only in 
the most desperate cases need loss of sight follow. 



260 ELECT1UCITY AND ITS 



CHAPTER XVIII. 



ELECTRIC WELDING. 



Electric Welding Machine. — The machine shown 
in the engraving on page 259 is for welding 3-inch 
extra heavy iron and steel pipe. 

The process of Electric Welding and Working 
of Metals, as invented by Prof. Elihu Thomson, 
has already been so far developed as to produce 
the most satisfactory results. Welding machines 
capable of uniting various sections of metals have 
been placed upon the market, giving manufactu- 
rers ample proof of their efficiency and economy, 
and already becoming a part of the necessary ma- 
chinery required in the various industries with 
which they are associated. 

The principle involved in this new art is that of 
causing currents of electricity to pass through the 
abutting ends of the pieces of metal which are to 
be welded, thereby generating heat at the point of 
contact, which also becomes the point of greatest 
resistance; while at the same time mechanical 
pressure is applied to force the parts together. As 
the current heats the metal at the junction to the 
welding temperature; the pressure follows up the 



RECENT APPLICATIONS. 



261 




262 ELECTRICITY AND ITS 

softening surface until a complete union or weld is 
effected, and as the heat is first developed in the 
interior of the parts to be welded, the interior of 
the joint is as efficiently united as the visible ex- 
terior. With such a method and apparatus, it is 
found possible to accomplish not only the common 
kinds of welding of iron and steel, but also of 
metals which have heretofore resisted attempts at 
welding, and have had to be brazed or soldered. 

Pieces of such metals and alloys as wrought 
iron, silver, copper, brass, lead, tin, zinc, bronze, 
German silver, platinum, gold, aluminium and even 
cast-iron, are not only welded to each other, but 
different metals can be welded one to another in 
many combinations, extending the applications of 
the process to the attainment of results hereto- 
fore impossible in metal-working. Solid iron or 
steel bars three inches thick are welded perfectly. 
The time consumed in making the weld of this 
size is from ioo to 120 seconds. 

The machines built by the Thomson Electric 
Welding Company are generators of electricity, so 
constructed as to produce in the most economical 
manner the low-pressure currents essential for 
welding and for similar work. They are of sizes 
and types suited to the kind and section of the 
metal to be worked. 

The dynamos are built to take power from any 
source, and the welding machines connected by 



RECENT APPLICATIONS. 26o 

ends are in contact an electric ring circuit is com- 
pleted, consisting of the part included within 
the primary coils, the clamps and metal to be weld- 
ed. The energy spent in this circuit is most easily 
regulated, and is thus adapted to the demands of 
the work to be done, whether it be thick or thin 
bars. None of the energy is wasted, and there is 
no expenditure at all when the welding is not in 
progress." 

The machines now being manufactured are so 
graded as to apply to various kinds of work, from 
the smallest wire to bars of over 3 inches in diam- 
eter. For heavier work, such as large forgings of 
locomotive frames, car axles, shafting, etc., special 
forms of machines adapted to the purpose will be 
supplied by the company, while by the use of spec- 
ially adapted holders and clamps applied to the 
standard forms of machines, various shapes and 
irregular sizes of metal pieces may be united with- 
out difficulty. 

The machinery which is used for producing cur- 
rents for welding, is also used with suitable electric 
devices, for electric soldering, brazing, shaping, 
forging, riveting, and bending of metals. 



264 ELECTRICITY AND ITS 



CHAPTER XIX. 

SOME MISCELLANEOUS ELECTRICAL INVENTIONS OF 
THE PRESENT DAY. 

Probably no other field, has produced so many 
new inventions within the last few years as the 
''electrical field.'' A large number of patents are 
being taken out every month on electrical appara- 
tus of all kinds, for use in almost every line of 
business. Among these the author has selected 
the following for description. 

A Novel Fire and Heat Alarm. — The accom- 
panying illustration shows the Iske automatic fire 
alarm, manufactured by Stoner, Myers & Co., of 
Lancaster, Pa. Fig. i shows the device with the 
gong and case removed, the clock work, and means 
of starting it being visible ; while Fig. 2 shows it 
as it appears hanging on the wall ready for use. 
The operation is as follows : The two cylinders 
shown at the bottom in Fig. 1, are connected by a 
tube which extends nearly to the bottom of the 
lower cylinder. This cylinder is partly filled with 
some liquid which will volatilize readily when re- 
lieved of pressure, and the whole (cylinders and 
tube) is exhausted of air, and hermetically sealed. 



RECENT APPLICATIONS. 



265 



It is then pivoted at some point on the tube so 
that the lower cylinder will just overbalance the 
upper, as shown. When, however, heat is applied, 
part of the liquid speedily evaporates, the pressure 
of the vapor forcing part of the remainder through 




Figure i. 



the tube, into the upper cylinder, when it immedi- 
ately overbalances the lower, and both rotate about 
the pivot. Their rotation is sufficient to set in 
motion the clockwork, and start the bell ringing. 



266 



ELECTRICITY AND ITS 



The device can, of course, be adapted to electric 
bells equally well: this is done by simply causing a 
small pin which is attached to the pivot, to make a 
contact and cause a circuit connected with an elec- 
tric battery and bell, which sets the bell to ringing, 




Figure 2. 



but where it is not desired to sound an alarm at a 
distance, the clockwork is held preferable, on ac- 
count of its simplicity, cheapness and portability. 
The clockwork is entirely encased by the gong, 



RECENT APPLICATIONS. 267 

and is wound by means of it, so that no key is re- 
quired. The alarms, unless specially ordered, are 
made to sound at i zo° Fahrenheit. 

The Otis Electric Elevator. — See illustration on 
page 268. Elevator machinery as a rule meets 
with the roughest manipulation while in use. No 
other apparatus operated by electric power is ex- 
posed to such strain — not even in street railway 
service, where, at least, the same operator is con- 
stantly in charge and a systematic inspection 
considered indispensable. 

By carefully considering these special conditions, 
this company has succeeded in perfecting an elec- 
tric elevator which is well suited to many places 
where it has heretofore been impracticable to use 
such an apparatus. The winding-machinery and 
safety appliances (including the Safety Governor, 
the Gravity Wedge Safety, the Automatic Stop- 
motion and the Slack-cable Stop ; also the devices 
for controlling the movement of the elevator-car) 
are such as they have been constantly building for 
the past twenty-five years ; consequently there are 
no experimental features. To give motion to the 
elevator machinery, they connect therewith, and 
make a part of the same, the very ingeniously con- 
structed motor (invented by Mr. Rudolph Eick- 
emeyer, of Yonkers, N. Y.) which possesses many 
novel and meritorius features, especially adapted to 
elevator-service, for which it is expressly designed. 



268 



ELECTRICITY AND ITS 



This motor, when so combined with the elevator, 
stops and starts with a gradual movement, and 
consumes power only in proportion to its load, and 




only while the elevator is in use, thus effecting the 
greatest economy in the consumption of power. It 
possesses in a high degree the best points of motor- 



RECENT APPLICATIONS 266 

construction, and a high efficiency is obtained. 
Simple and accessible in all its parts, of the best 
material to meet electrical and mechanical require- 
ments, it is also protected by its unique construe- 
tion, which makes the motor completely iron-clad 
without adding any unnecessary weight. It has, 
further, the special advantage of a powerful field 
and the shortest possible magnetic circuit, which 
entirely prevents " sparking" at the commutator, 
and affords perfect self -regulation. It may also be 
added that, although it possesses a very strong 
magnetic field, yet there is no external magnetism 
in the machine. The motor is so coupled to the 
elevator-gear that it starts and stops with the wind- 
ing-machinery, the whole being under perfect 
control of the operator in the car, thus forming a 
self-contained apparatus, free from jerky and 
irregular running of detached gearing, as when 
operated by belts. 

The difficulties heretofore experienced from 
heating or " burning out" have been effectually 
guarded against in this machine ; and, in connec- 
tion with the operating device, they employ an 
indicator which at all times shows the operator in 
the car the exact position of the controlling and 
and reversing-switch on the motor. 

The Home Electro-Medical Apparatus is shown 
on page 270. For doctor or patient, this electro 



270 



ELECTKICITY AND ITS 



medical apparatus is the most convenient and 
reliable. It is reliable because with its Dry 
Battery so much less care is necessary to avoid 
getting it out of order. The entire absence of 
acids, liquids or salts, will be appreciated by any 
one who has ever had occasion to use a medical 
battery. The box when closed up may lie in any 




THE HOME ELECTRO-MEDICAL APPARATUS. 

position on a table or shelf, or in the bottom of a 
carriage without harm. 

The strength of the various currents ranges 
from those which are so mild as to be scarcely per- 
ceptible, to the most powerful that can be endured 
by a strong man. 

The appliances furnished with the apparatus 



RECENT APPLICATIONS. 271 

consist of foot-plate, sponge, cords, and handles 
(electrodes). The electrode having a wooden 
handle is used as a sponge-holder when required. 
The sponge is held by it, by pressing part of the. 
moistened sponge in the hollow tube of the elec- 
trode. The small switch at the left-hand end of 
the base is turned to the left to put the battery in 
operation. When this is done, if the spring at the 
left-hand end of the coil does not at once vibrate 
it should be given a slight impulse with the finger, 
and it will continue to vibrate with the power of 
the battery, if the screw is turned to its proper 
position. This can be ascertained by turning it 
forward or back. 

If for any reason it is desired to take out the 
battery, this can be readily done by loosening the 
screws which clamp its poles to the flat upright 
pieces, when the battery cell can then be lifted out 
of the plated cup, on lifting the latter, which is 
hinged to an upright positon. In returning the 
battery to its position, notice that the carbon pole 
belongs and fits to the flat upright at the back of 
the base, and the zinc pole fits the upright nearest 
to you. 



272 ELECTKICITY AND ITS 



CHAPTER XX. 



ELECTRO-PLATING. 



The author will not attempt to give any practi- 
cal directions for electro-plating, the space allotted 
to this subject being too small, but will simply de- 
scribe the process in a general way so that the 
reader may have a fair understanding of the prin- 
ciple. Should he wish for a more practical knowl- 
edge, he may find a number of good works on the 
subject in almost any book store. 

This .art was discovered by Dr. Wollaston in the 
year 1801. He observed that a piece of silver 
immersed in a copper solution when connected with 
a more positive metal became coated with copper. 
But it was not until the year oi 1 840 that electro- 
plating came into commercial use, being introduced 
at that time by Messrs. Elkingtons. 

The present process of electro-plating consists 
of placing an "anode" and the article to be plated 
in the plating bath and causing a current of elec- 
tricity to pass from one to the other through the 
plating solution; this causes the anode to dissolve 
and then to be deposited on to the surface of the 
article. The necessary current may be supplied 



RECENT APPLICATIONS. 



StfS 



18 




274 ELECTRICITY AND ITS 

by an electric battery or a dynamo, of course 
depending on the strength of the current required. 

Fig. i shows an electric battery and a plating 
vat containing the silver solution. The anode 
which is a plate of pure silver is suspended from 
the rod connected to the positive pole of the bat- 
tery, the article to be plated being suspended to 
the rod connected to the negative pole. The 
silver solution is the double cyanide of silver and 
potassium. The addition of a minute trace of 
bisulphide of carbon to the solution will cause the 
deposited metal to have a bright surface. Should 
the current be too strong and the deposition too 
rapid, the deposited metal will be greyish and 
crystalline. 

Articles to be plated should first be cleaned by 
washing in soap and hot water, and then rubbed 
perfectly dry. In gold or silver plating iron ob- 
jects, they should first be given a thin coating of 
copper. 

Gold solution is usually worked warm. Articles 
after being plated are polished by a burnisher, 
brushes, dry flannel and chamois skin, 



RECENT APPLICATIONS. 275 



CHAPTER XXI. 

ELECTRIC GAS LIGHTING APPARATUS. 

Now that Electric Gas Lighting and Bel] 
Bitting has become a universal need, the following 
directions will not come amiss. Where a compe- 
tent electrician can be employed it will be better 
to employ one, but in case it is impossible to do so 
the amateur may, by following the directions here 
given, do a very good piece of work. 

DIRECTIONS FOR SETTING UP AND MAINTAINING BATTERIES. 

Crowfoot Gravity Battery. — Open out the cop- 
per, so as to present all of its surface to the action 
of the solution, place it in the bottom of the jar, 
run the insulated wire out of the top of the jar for 
connecting up. Suspend the zinc above the copper 
by hanging the hooked neck on the rim of the 
glass. The neck of the zinc is provided with a 
connecting clamp to receive the wire from the 
copper of the next cell. Pour clean soft water 
into the jar until it covers the zinc, then drop in 
six or eight ounces of copper sulphate (blue 
vitriol) in small crystals. Connect the battery 
/ for ordinary purposes ) zinc of one cell to copper 



276 ELECTRICITY AND ITS 

of the next and so on, and connect the two elec- 
trodes of the series and let them so remain for a 
few hours, until the separation of the two solutions 
which will be known by the blue observed in the 
bottom of copper solution. This "blue line ,, 
should be maintained midway between the zinc and 
copper ; when it is too low, drop in a few crystals 
of copper sulphate, when too high, connect the 
battery in short circuit as before described until it 
goes down. While the battery remains in action 
there is an increase in quantity of zinc sulphate 
solution in the upper part of the jar. The specific 
gravity of this solution should be maintained at 
25 ° ; when the hydrometer indicates a lower 
degree there is too little zinc sulphate solution, 
when a higher degree than 25 ° there is too much 
zinc sulphate, and a portion of it must be taken 
out; and that remaining diluted with pure water. 
When zinc oxide forms on the surface of the zinc, 
it must be taken out and washed in clean water with 
a brush. 

Daniell Battery, — Fill the jar and porous cell 
with water and the pocket with copper sulphate. 
The directions for Gravity Battery will apply to 
the maintenance of the Daniell. 

Samson Battery. — Directions for setting up and 
using. — Put six ounces of Sal Ammoniac in a glass 
jar, fill one-third full of warm water, and stir well 



BECENT APPLICATIONS. 277 

Clean, soft water is preferable. Use no more 
Sal Ammoniac than will readily dissolve. 

Insert the Carbon Vase and Cylindrical Zinc, 
taking care that carbon is insulated from Zinc by 
cover and rubber band. See that cover fits down 
over the Carbon into its place in neck of jar ; only 
one rubber band is required, say an inch from 
bottom of Carbon. When the Battery is set up, 
the solution should not quite reach the lower line 
of paraffin around neck of jar. 

The Battery should be put in a cool, dry place. 
See that connections are clean and firmly made, 
and that the connecting wires are properly insu- 
lated. 

When you add Sal Ammoniac or water to make 
good any loss by evaporation, take out both 
Carbon and Zinc, and keep top of jar dry. It is 
better not to add Sal Ammoniac to an old solution, 
but rather to use a little water and stir well. 

When the battery fails to work properly, throw 
out the solution, clean Carbon, Zinc and connec- 
tions ; let the Carbon stand in a warm place until 
old solution leaks out — if possible let it dry 
through — then set up the Battery with fresh 
solution. 

When exhausted from overwork or repeated 
grounds, clean the Carbon, let it soak half an hour 
in hot water, give it a day or two of rest in the sun 



278 ELECTRICITY AND ITS 

or other warm place, and it will again show up its 
full strength. 

Lee lane he Battery. — Directions for setting up. — 
Put six ounces of Sal Ammoniac in a glass jar, add 
water enough to fill the jar about one-third full, 
stir this until it dissolves, pour a little of this solu- 
tion into the porous cup, put the cup and zinc int^ 
the jar, and connect the battery as usual. 

Grenet Battery, to Make Solution. — To three 
pints of cold water, add five fluid ounces of sulphu- 
ric acid ; when this becomes cold, add six ounces 
( or as much as the solution will dissolve ) of finely 
pulverized bichromate of potash. Mix well. 

To Charge the Battery. — Pour the above solu- 
tion into the glass cell until is nearly reaches the 
top of the spherical part ; then draw up the zinc 
and place the element in the cell. The fluid 
should not quite reach the zinc when it is drawn 
up. 

Carbon Battery. — Fill the glass jar with water ; 
the porous cell with electropoion fluid. The 
height of the liquid in the jar and the porous cells 
should be about the same. 

Directions for making " Electropoion Fluid" for 
Carbo7i Battery. — Mix one gallon sulphuric acid 



RECENT APPLICATIONS. 279 

and three gallons of water. Then, in a separate 
vessel, dissolve six pounds of bichromate of pot. 
?.sh in two gallons of boiling water, mixing the 
whole thoroughly together. When cold it is ready 



To Amalgamate Zincs. — This may be very well 
aone by first immersing the zinc in a solution of 
dilute sulphuric acid and then in a bath of mercury. 
A brush or cloth may be used to rub them, so as 
to reach all points of the surface. 

The Fuller Mercury Bicromate Battery. — Amal- 
gamate the zinc and its copper rod in the usual 
way. Place the zinc in the porous cells and pour 
into the latter a tablespoonful of mercury. Fill 
the porous cell with water to within about two 
inches from the top, Place the porous cell and the 
carbon in their positions in the jar as shown in the 
cut of the battery. Then fill the jar to within two 
or two and a half inches of the top, with a mixture 
o* three parts of electropoion to two parts of water. 
The zinc should be lifted out occasionally and the 
sulphate washed off. Keep a supply of mercury 
in the porous cell so as to have the zinc always 
well amalgamated. If the battery does little work 
it will last three or four months without being: 
touched. To renew, clean all deposits from carbon 
and zinc, and set up with fresh solutions as above. 



280 ELECTRICITY AND ITS 

HOW TO PUT UP AUTOMATIC GAS BURNERS. 

The battery to be used is some form of open 
circuit, preferably the Samson on Leclanche 
Disque. Place the battery, consisting of four or 
six cells, according to size of the house or number 
of burners to be used, in the cellar or lower hall- 
way, taking care to select a place of uniformly cool 
temperature. The place selected should not be 
too dry, for a dry atmosphere tends to evaporate 
the fluids too rapidly ; nor very damp, as too much 
moisture interferes with the action of the battery. 

To Connect the Battery. — Connect the zinc of 
one cell with No. 16 or 18 wire to the nearest gas 
pipe on the house side of the gas meter. To make 
contact with the gas pipe perfect, file a bright 
surface on it and wind the bared copper wire 
around it several times. After the cells have been 
joined together, carbon of one to zinc of next, run 
a wire from the last carbon through the one-point 
switch, located near the battery, to the spark-coil; 
then from the spark-coil make connection to .the 
bunch of wires which lead to the various rooms of 
the house. 

To Detect a Ground. — Disconnect the battery 
wire from the bunch of wires in the cellar and 
touch each house wire with it separately. The 
grounded wire will be detected by a spark and 



RECENT APPLICATIONS. 281 

should then be left out of the bunch of wires, 
which may now be connected with the battery 
wire again. The fixtures to which the grounded 
wire runs should be carefully examined, as the 
trouble is most likely to be in the fixture wiring or 
where the connection is made back of the wall 
plate. If, however, the trouble is between the 
fixture and the cellar, a new wire should be run. 
After the trouble is removed connect the wire 
with the bunch of wires as before. 

For Automatic Burners, run wires from the 
cellar ( where connection is made to battery wire ) 
to the centre brass strips on the rear of the key, 
or press-button plate. Run wires from the other 
points of the press-button plate to the automatic 
burner, which is to be governed from that point, 
and connect the wire from the black press-button 
to the electro-magnet which shuts off, and the wire 
from the white press-button to that which turns on 
the gas. The circuit for lighting is made from 
battery, through switch, spark-coil, wire, brass, 
strip on press-button plate, by pressing the white 
button, through the electro-magne* which turns on 
the gas ; wire at the tip of the burner ( by the 
union and parting of these wires the igniting spark 
is made), thence to the gas pipe, and back to 
battery. For shutting off, the same circuit is 
made, except that by pressing the black button the 



282 



ELECTRICITY AND ITS 



circuit is closed through the other electro-magnet 
in the automatic, thus shutting off the gas. 

Volunteer Pendent Banter, — The first pull turns 
on and ignites the gas, and holds the arm in the 
slot ; the second pull releases the arm and extin- 




VOLUNTEER PENDENT BURNER. 

guishes the gas. From the position of the arm it 
can be readily ascertained whether the gas is on 
or off. 

The Advance Welsbach Burner. — The Advance 
Attachment is an adaptation of the Regular Ad- 
vance burner in order to make it available for use 



RECEXT APPLICATIONS. 



283 



with the Welsbach and similar burners. Owing 
to the construction of incandescent gas-burners, it 
is necessary to light them from below by means of 
a small gas flame which 
issues from a pilot tube 
at the side and just 
beneath the main burn- 
er. By turning a key 
(just as a common gas- 
key is turned) the en- 
tire operation is accom- 
plished. As the key 
is turned, the gas is 
at once turned on, both 
in the main burner and 
in the pilot tube ; the 
electrodes meet and 
light the gas at the 
pilot tube, this flame 
instantly reaches up 
to and ignites the main 
burner, the pilot tube 
is then extinguished, 
leaving the main gas- 
way open and the light 
burning. A reverse motion of the key turns 
out the light. 

The important features of this attachment are 




284 



ELECTRICITY AND ITS 



that it does not short-circuit, owing to an ingeni- 
ous arrangement of the movable electrode ; and it 
avoids breaking of the mantles because of the 
smooth, easy method of ignition. 

The "Advance " Automatic Burner.— There are 
two double magnets operating two armatures, which 




throw off and on the valve and at the same time 
raise the spark contact. The throwing off of the 
valve is controlled by the armature acting on a 
single pin in the head of the valve plug. 

The Thumb-Cock Burner, here shown, has an 
attachment upon the small end of the gas-cock, 



RECENT APPLICATIONS. 285 

located in the base of the burner, consisting 
of a vibrating arm with an elongated hole, tripping- 
pin and cam. By the opening movement of the 
gas-cock the vibrating arm, with its elastic contact 
point, is forced against and past the fixed electrode, 
tripped and returned by means of the retractile 
spring, leaving the gas turned on and lighted, — a 
quarter turn of the thumb-cock backward extin- 




THUMB-COCK BURNER. 



guishes the gas. The operation is such that short- 
circuiting at the electrodes is next to impossible. 

TO PUT UP THE HAND-LIGHTER. 

Run a single wire from the battery as with the 
Automatic, and connect it with the binding screw 
on the insulated collar at the tip of the burner. 
The movement of the pending chain brings the 
spring wire at the end of the movable arm into 
connection with the fixed electrode on the insu- 
lated collar, closing the electrical circuit, the sub- 



286 ELECTRICITY AND ITS 

sequent breaking of which produces the igniting 
flash or spark. 

GENERAL DIRECTIONS. 

Switches. — A switch near the battery is useful, 
so that in case of any trouble the occupants of the 
house can switch off the battery and save it from 
running down. 

Spark-coil. — An eight or ten-inch spark-coil is 
sufficient for lighting coal-gas. 

Connections. — Simply winding the wire is not 
sufficient to produce a perfect connection ; solder- 
ing is necessary, and rosin, not acid, should be 
used. 

Insulation. — Particular care should be exercised 
in every part of a job, that perfect insulation be 
obtained. Any leakage will rapidly destroy the 
efficiency of the battery. Every foot of wire 
should be closely examined before being run, and 
all suspicious places wound with the rubber tape. 

Running Wire in Damp Places. — Extra care 
should be taken in running wires through damp 
places. For walls and other equally bad sections, 
rubber-covered wire is good. Where tacks are 
used, the wire should be covered with rubber tape. 
Steam or hot water pipes should never be crossed, 



RECENT APPLICATIONS. 287 

except that extra care be taken that the wires do 
not come in contact with them, as the heat melts: 
the paraffin on the covering of the wire and 
destroys the insulation, often causing a ground. 

Hints for Running Wires out of Sight. — From 
key or press-button plate on the wall to the floor. 
Punch a hole through the plastering at the required 
position, being careful that there is no studding at 
that place. Use a brad-awl, and cut the hole 
large enough to set in the press-button plat~. 
With a few inches of small brass spring wire, push 
through the opening a few inches of No. 19 double 
jack-chain, such as is used for general fishing 
purposes, first having connected the end of the 
chain with a piece of heavy linen thread. Run 
out the thread until the chain touches the floor 
beneath (between the laths and the outside wall) ; 
move the thread and locate the chain by sound. 
Bore a hole through the base-board or floor, as the 
case may be, towards the chain. Use a two or 
three-foot German twist gimlet. With a small 
brass spring wire, bent at the end in the shape of 
a hook, fish for the chain and draw it out. At the 
other end of the thread attach the wire and draw 
it through with the thread. Passing under the 
floor, bore a second hole through the floor as near 
the other as possible. Run into this a piece of 
snake or fishing wire ( which is x ^ inch steel 



288 ELECTRICITY AND ITS 

wire, with a hook at the end ), until it comes to an 
obstruction. Locate the obstruction by sound. 
In running wires under the flooring, first carefully 
examine all parts and find the direction in which 
the beams and timbers run, and run wires parallel 
with these. After locating the end of the fishing 
wire, see if the obstruction be a timber; if so, 
find the centre and bore from the middle diagonally 
through it in the direction of the fishing wire. 
Drop a jack-chain and thread through the hole ; 
fish for it and draw it through hole No. 2, attach 
the insulated wire and draw it back. Starting 
at hole No. 3, bore hole No. 4 diagonally through 
the timber in the direction in which the wire is to 
be run, making holes Nos. 3 and 4 form an 
inverted V through the timber. Run the fishing 
wire through hole No. 4, until it meets an obstruc- 
tion. If at the end of the room, bore through the 
floor, drop chain, fish it out, attach wire, and draw 
it home. Putty up holes after having done with 
them ; or in case of hard finish, plug them up with 
wood. In lightly built houses it is often found 
easier to take off the moulding above the base- 
board and run the wire under it. In such cases 
care should be taken to break off the old nails, as 
any attempt to drive them out would cause a bad 
break. In closets and around chimneys it is 
usually found easy to work. A mouse or lead 
weight attached to a string may often be dropped 



RECENT APPLICATIONS. 289 

from the attic to the cellar ceiling through the 
space outside the chimney. It is well before 
starting on a job to carefully examine the whole 
house, and find the easiest places to run in. When 
necessary to take up carpets, be sure to put them 
down again as quickly as possible, in order to 
reduce to a minimum the inconvenience to resi- 
dents. 

WIRING FIXTURES. 

Where it is impossible to run the wire between 
the gas pipe and the outer shell, run it above if the 
fixtures be overhead ; below if the fixtures be low 
down, and bind the wire close to the fixture with 
fine thread, being sure that the sharp corners will 
not cut through the insulation and eventually 
cause a ground. Shellac the wire to the pipe, and 
when hard, remove the thread. At the joints or 
hinges connect the nearest set points by means of 
a wire loop of sufficient size to in no way interfere 
with the action of the fixture, and wind the 
insulated wire around this loop in the form of a 
spiral. Great care should be taken that perfect 
insulation be obtained, and in all such parts the 
wire should be covered with rubber tape. In 
running wire between the gas pipe and the outside 
shell, the same care should be exercised to guard 
against grounding. To pass the rings and other 
sections where there is not sufficient space, bore 

19 



290 ELECTRICITY AND ITS 

through with a small monkey -drill, or punch a hole 
with a brad-awl, or file off sufficient metal to allow 
an exit ; if necessary, run the wire through and 
over the obstruction. Rubber tape must be used 
wherever the wire passes near the metal of the 
fixture or is liable to touch it. 

The Best Time to Wire a House is when the 
builders have finished boarding in and have not 
yet commenced lathing. The cost of wiring at 
that time is very much less, sometimes not more 
than one-half as much as in the finished structure. 
In houses already occupied, the inconvenience 
caused by putting in wires is slight. Little or no 
dirt need be made; there need be no hammering 
and pulling away plastering, laths and floors. The 
most expensive finishing should in no way be 
injured by the workmen. When the job is com- 
plete and well done, it will be difficult to discover 
evidence of the work having been done. 

TOOLS AND MATERIALS NECESSARY FOR WIRING A HOUSE. 

Rubber Tape, for winding wire where tacks are 
driven for holding wire overhead — to insure 
perfect insulation, and prevent breaking through 
because of sharp edges. 

Tags, for numbering wires at the battery. 



RECENT APPLICATIONS. 291 

Double-pointed Tacks, for holding up wire. Use 
as few as possible. 

Brass Spring Wire. A few inches for pushing 
chain through holes. 

Steel Spring or Snake Wire, for fishing pur- 
poses. Fifty feet is sufficient. 

No. 19 Double Jack Chain. A small amount 
for dropping purposes. 

Common Brad Awls, for punching holes through 
walls, etc. 

German Twist Gimlets, two and three feet 
long, \ or T 5 g- in., for boring purposes. 

Rat-tail File, for filing holes through fixtures 
and other metal. 

Monkey Drill, for drilling through metals. 

Wire. No. 16 or 18 braided wire is heavy- 
enough, if it is well insulated. Great care should 
be taken in examining the wire to see that it is 
thoroughly insulated, as more depends upon this 
than any other feature of the job. The larger the 
wire, the less the resistance. 

The reader can form from a diagram on next 
page, and plan on page 293, a very good idea 
of how to wire a house for Electric Gas Lighting. 



292 



ELECTRICITY AND ITS 




/ JZ 



DIAGRAM FOR WIRING A HOUSE. 



BECENT APPLICATIONS. 293 



PLAN FOR WIRING A HOUSE. 

1 Battery on Shelf. 

2 Spark-coil. 

3 Galvanometer. 

4 Switch-board, with Individual Switches. 

5 Gas-meter. 

6 Connection of wire from battery with gas-pipe on house 

side of meter. 

7 Gas-pipe. 

8 Automatic in room S. 

9 Press-button or key-plate for lighting No. 8 
io-ii Press-button for key-plate Automatic No. 12. 
13 Pendant Chain of Hand-Lighter. 

15 „ Loop for passing wire around joint in fixture 

16 Switch for first floor. 

17 Switch for second floor. 

18 Switch for third floor. 

19 Gimlet, showing direction of holes for running wires oui 

of sight. 

20 Beams, with wires run through them. 

21 Showing manner of carrying wire around corner of room 

below, bringing it through hole and then dropping it 
back into position. 

22 Part of Automatic, with Electro-magnet, showing the 

shut-off. 

23 The same, showing the turning on and lighting. 

24 Showing how to run wire between gas-pipe and fancy 

covering of fixture. 
2q Four press-button plate, lighting Nos. 26 and 27. 



294 ELECTRICITY AND ITS 



CHAPTER XXII. 

ELECTRICAL MEASUREMENT. 

Before commencing our description of the 
measuring instruments and their uses, we will take 
a brief survey of the quantities to be measured. 
Electricity requires a "push" to force it over 
the conductors, just as water and steam require a 
pressure to make them flow through pipes. This 
push is called the Electro-motive Force, or the 
E. M. F, of the circuit and is measured in volts. 

We speak of electrical quantity just as we do of 
water quantity. The latter is measured in gallons 
and the former in coulombs. The coulumb is not 
used much in practical work, but in its stead we 
have the ampere which is the unit of the rate of 
flow of electricity and is equal to one coulomb per 
second. The flow of electricity is attended with 
friction or resistance, just as the movement of 
water in a pipe, and we have a unit to measure 
this resistance called the ohm. These units are 
all dependent upon and bear a fixed relation to one 
another. This relation is expressed by Ohm's Law 
which says in substance that the current over a 



RECENT APPLICATIONS. 295 

given conductor is equal to the E. M. F., acting 
upon it divided by its resistance. 

Algebraically this is C = | . 

Where C = current in amperes, E= E. M. F. 
in volts and R= resistance in ohms. By a slight 
transformation of the above equation we can get 
the value of the E. M. F., or the resistance in 
terms of the other two quantities. 

The three are given below : 

Amperes= Volts-f-Ohms. 

Volts= Amperes X Ohms. 

Ohms= Volts-f-AmpereSo 

As an example of the application of the formulae, 
suppose we have an incandescent lamp running 
upon a no volt circuit, and suppose its hot resist- 
ance is 200 ohms, required the current passing 
through it. 1 10-^200^.55, or the lamp uses .55 
amperes. 

These three electrical units are all that are used 
much in practical work, and are all that need be 
described here. There is however one mechanical 
unit, the watt, which is used very often in connec- 
tion with these. It is the unit of the rate of the 
expenditure of energy and is of the same nature as 
the horse-power but smaller. Seven hundred and 
forty-six watts equal one horse-power. We may 
find the watts used in a circuit by three formulae 
with the above units. 

Watts = Amperes (squared )X Ohms. 



296 ELECTRICITY AND ITS 

Watts = Amperes X Volts. 

Watts = Volts (squared)-^- Ohms. 

As an example, what is the horse-power used in 
an arc lamp running on a 10 ampere circuit at a 
pressure of 50 volts ? 

10X50=500 Watts. 

500-^-746= .6 J horse-power. 

Measuring Instruments. — Electrical test instru- 
ments which are intended for anything more than 
to indicate the presence and direction of the 
current or make comparative measurements of its 
value must be " calibrated. " This is generally 
done by comparison with a standard. Unless 
there is something of this sort accessible it is not 
much use for the amateur to try to do anything in 
the way of making electrical measuring instru- 
ments. Moreover, he must not expect to produce 
an instrument that can be relied upon for very 
accurate work. This is only done by the best 
instrument makers and with high-priced articles. 

In what follows we shall describe apparatus 
suitable only for rough work, but this must not be 
taken as implying that it may be carelessly con- 
structed. The small extra trouble in doing the 
work conscientiously will save an endless amount 
of annoyance when you come to use it. 

The Bridge. — This piece of apparatus comes 
first upon our list, as it is used perhaps more than 
either of the others and often in conjunction with 



RECENT APPLICATIONS. 297 

them. The one we shall describe is but a slide- 
wire bridge, not the ordinary Kirchhoff pattern. 
It is a modification due to Cardew, which is direct 
reading, and so does away with the troublesome 
calculations incident to the working of the other. 





y vy gg \iy wy yvy v y v* y g k . V* gg y g y v ; y v SSSS 



^ 



Figure i. 

Figure i gives a general view of the bridge 
when complete. In the middle is a stick of hard, 
well-seasoned wood, 24 inches long, 1 y z wide, and 
1 high. Into each side a slot is cut, by running 
the piece over a circular saw, for guides for the 
rider. The slot should be % of an inch from the 
top. The rider itself is made from sheet brass, 
3 T 2 inch thick cut and bent into the form shown 
in Fig. 2. 

The guides G must fit into the slots cut into 
the sides of the piece of wood described above and 
the body of the slider clear the top of the wood 
strip by }& of an inch. An index I, is cut and 
bent down as shown and has«its end beveled and 
a small mark on it. This end runs close to the 
scale which will be put in the wooden strip and 



298 



ELECTRICITY AND ITS 



the mark is to read from. To prevent side motion 
one side of the slider is cut and bent inwards just 
far enough to press firmly upon the sides of the 
strip. On top a piece of light spring brass is 
soldered and has a button and a brass contact 
piece fastened to the end. The end of the contact 
piece is filed to a chisel-shaped edge, not sharp 




Figure 2. 



nowever, and a small notch is made in this edge 
to receive the wire when it is pressed down on it. 
In its normal position the contact should clear the 
wire by about a x \ of an inch. It is guided of 
course by the hole through which it passes in the 
top of the slider. 

Make a wooden base for the instrument 30 inches 
long, 6 inches wide and % inch thick. Screw 



RECENT APPLICATIONS. 299 

the wooden strip to this base so that it will be in 
the middle of the length of the board and I inch, 
from one side. Place two binding posts at one 
end of your board for your unknown resistance. 
They should be fairly good-sized, so that the 
contact error in them may be small. For your 
slide wire use a piece of No. 25 German silver or 
Platinum wire. The latter is preferable on 
account of its greater resistance and smaller tem- 
perature error. Fasten one end of this to one of 
your binding posts on the under side. This must 
be done very securely, and a drop of solder will 
insure its staying. Then carry your wire up 
through a hole in the base-board at one end of the 
strip, over the top of the strip, along its length, 
and down the other end. Draw it tightly and 
take a turn around a screw to hold it in place and 
then carry the wire up and down the length of the 
board three times, taking it around a screw-head at 
each end to hold it taut and finally take it through 
another hole in the base-board and secure it to the 
other binding post. Wherever the wire goes on 
the under side of the board, it must be run in a 
groove to prevent its being caught and pulled 
when the instrument is moved around. Following 
is a skeleton diagram of the bridge. See Fig. 3. 
A and b represent the proportional arms; e 
represents that part of the wire from the binding 
post to end of the movement of the slider ; d 



500 



ELECTRICITY AND ITS 



represents the range of the slider and c is meas- 
ured from e to b ; x is of. course the resistance to 
be measured. 

You must first determine the ran^e of readings 
you desire. From zero to ioo ohms is a conven- 
ient position. Then measure by some ot^er bridge 
as accurately as you can e and d. It can easily be 
shown by algebra that the ratio 

b : a : : d : x — d 



*\ 




Figure 3. 

X in this case being the higher limit of your 
bridge. Besides determining the ratio b to a this 
shows that the resistance d must be less than your 
higher limit or the bridge won't work. The most 
sensitive point is of course where x is doubled. 
With this ratio we easily determine the value of c 
from the following equation : 



BECENT APPLICATIONS. 301 

or in other words the sum of the resistance of the 
higher limit and that of e multiplied by the ratio 
found above of b to a is equal to the resistance 
of c. Measure off this resistance on your wire and 
mark the point on the board near the wire. 
Divide up the remaining portion of the wire pro- 
portionally to a and b and mark the position of the 
division on the board. You will need four more 
binding posts on your board which you can put on 
the back side, out of the way. A plan view of the 
bridge is given below, showing how to make the 
connections. See Fig. 4. 



Unknown. 
Res /stance 





BiATTCJfy 




GlLfANOMETEf) 




^— 

0-= '- 




-V^= 


N> 

'J 


* 




^Zj 


0— 


iii[iMiiiiiiiii l iMi.MiM ll iiiiiiiiNi[ l iiiiMiiiiiiiiiiii"MiiiiiiiMiiniiiiiiinimigMniHi]iiimiin 


IfH 







Plan of Br/dge> 

Figure 4. 

The slider is connected to the galvanometer 
binding post by a thin, flexible conductor, and the 
other binding posts connected to the division 
points you marked above, and soldered. If every- 
thing had been accurately done the bridge would 
now be ready for use, but as it is impossible to do 
this exactly, we will have to go over it again to 
make the final adjustment. We will first, how 



302 



ELECTRICITY AND ITS 



ever describe the galvanometer to be used with it. 
This is to be made after what is known as the 
D' Arsonval pattern, with a coil suspended between 
the limbs of a permanent magnet. See Fig. 5, 
Wind the coil in a former made of thin sheel 
copper* bent and soldered together in the form oi 
a rectangle with the corners cut off and the edges 
turned up. Make this rectangle 2 inches long and 
\y 2 inches wide and y 2 inch thick, and insulate 
the channel, wnere the wire is to be, thoroughly 




Figure 5. 

with paper and shellac. Make a small hole in 
the bottom of the channel and pass the starting 
end through this into the inside of the rectangle 
and then wind on the wire. Use for this purpose 
No. 32 silk-covered copper wire, and wind on until 
you have a coil about }& of an inch thick, and 
shellac it well, and afterwards dry it in a warm 
oven. To suspend the coil make two little hooks 
out of brass wire and solder them to two small 



RECENT APPLICATIONS. 303 

square plates of sheet brass or copper. See Fig. 6. 

Solder one end of your wire to one of these 
plates, and the other end to the other plate and 
bind the plates firmly to the opposite ends of the 
coil, as shown in the general drawing by strong 
flax thread, insulating them of course carefully 
from the coil beneath them and the copper former. 

Make the magnet of the best steel you can get. 
What is known as tungsten steel will give the best 
results if you can obtain it. Its cross section 
should be somewhere near i}4"XH" an d it should 
be bent as the sketch shows, leaving the opening 



i 



Figure 6. 

between the poles y%' r wider than your coil and the 
length of the poles themselves about the length of 
the coils. Fig. 7. 

In the middle of the top, drill a }i" hole and 
make a plug with a milled head to fit it snugly and 
solder a small hook to the lower end of the plug 
Make your magnet glass hard, and strongly mag* 
netise it by current in a helix of wire. The better 
and stronger your magnet is, the more sensitive 
will be the galvanometer and the less will it be 



304 



3LECTRICITY AND ITS 



affected by outside disturbances. To increase the 
strength of the field make a core out of a piece of 
soft bar iron, which will go inside the coil and 
allow it to move freely. You will need a small 
mirror to attach to the coil. This can be made, 
but it is much better to buy it of a dealer in 
instrument supplies. The glass must be very thin 
and true. It can be fastened to the wire on which 
the hook is bent by sealing-wax. The accompany- 
ing sketch shews a galvanometer set up, but with 
one half removed for the sake of clearness. See 
Fig. 8. 




Figure 7. 

Fasten the magnet to your base-board by means 
of brass angles. On the under side of the board 
cut out a place for the tension spring, which must 
be fastened to the board at one end, and at the 
other have a hook to engage with that on the coil. 
A small screw passing through the board and 



KECENT APPLICATIONS. 



305 



bearing on the spring will serve to regulate the 
tension. Make a link of fine brass wire with an 
eye in each end to suspend the coil from, and hang 




//f^o/f. 



/fo/v Co/ft 



Figure 8. 



it with the coil from the plug as shown. The plug 
will serve to bring the coil to zero if it should get 
displaced. The core is to be fastened to a block 
behind, which is shown in section, and must leave 
the coil free to rotate about the suspension, for 



20 



306 ELECTRICITY AND ITS 

30° or 40°. Two binding posts will be needed, 
one to connect with the tension spring and the 
other with the magnet or the plug on top. On 
passing a current through the galvanometer the 
coil should deflect to one side or the other, accord- 
ing to the direction of the current. The currents 
we shall use in connection with the bridge will 
often be too small to give a deflection of the coil 
readily apparent to the eye, so we must arrange 
some means of detecting its movement. This can 
be done with a telescope, but as this instrument is 
not often found outside of laboratories, we will 
describe the apparatus for using a spot of light. 

Unless you have a pretty dark corner in which 
to set up your instrument, you had perhaps better 
build a large box (or a frame and cover it with 
cloth), about 2 feet high, 3 wide and 3 long. 
Leave one end open and at the other mount a 
paper scale, divided decimally, and the divisions 
not much smaller than T y. Make the scale 
2y 2 feet long. Just under the scale make an 
opening 1^X2^ to let the light of the flame 
through. The flame itself can be an ordinary 
kerosene lamp with a guard made of tin around the 
chimney, with several slits of varying widths cut 
in it. See Fig. 9. 

Set up the galvanometer in the open end of the 
box with the mirror facing the other end. Place 
your lamp behind the opening, so that the light 



KECENT APPLICATIONS. 



307 



from it will fall upon the mirror and be reflected 
upon the scale. The slip in the lamp guard should 
be well defined upon the scale, and unless you 
have the luck to get just the right kind of mirror, 
you may have to interpose a lens between it and 
the lamp to make the inflected image sharp. See 
Fig. 10. 

Now when you pass a current through the 
instrument too small to give a perceptible deflec- 



W 



1_M 



WJ 



FlGUEE Q. 

tion, it will be shown by this arrangement as you 
have practically increased the length of the lever 
arm and doubled the angle of its movement. 
Almost any kind of battery will do for this, pro- 
vided it gives sufficient voltage. As you are not 
using the battery constantly, one of the "open 
circuit " type will answer very well. If you expect 
to have your instrument portable there are some 
dry batteries made which answer excellently for 
this purpose. 



308 



ELECTHICITY AND ITS 



We will now go back to the bridge. You 
should have a resistance measured off on some 
other bridge, which you can rely upon equal to the 
highest you expect to measure on your bridge. 
Put this between the "unknown" binding posts 
and connect your battery and galvanometer to 



C*'""*^ 



0^::: 




Zam^o 



Figure io. 

their respective places. You should have a key in 
your battery circuit. It might well be placed per- 
manently upon the bridge board. Adjust the 
reflected image to the middle of the scale by the 
plug at the top of the galvanometer. Press your 
battery key, and after placing your slider about 
where you wish your highest measurement to 
come, press its key also and watch its reflected 
iight. It will probably move to one side or the 
other, in which case shift your slider back and 



BECENT AFPlACATIuAoc 309 

forth until the light comes to rest *¥ou must of 
course never allow the contact piece to scrape over 
the wire, but first make your adjustment and then 
press the key. If the place where your light 
comes to, does not move, upon depressing the key, 
and is near enough on the slider scale to the place 
where you wish your highest mark to be, let it go 
and try the lowest. If not you will have to shift 
your soldered connections a little until it does come 
right, being careful each time to allow the wire to 
cool before making the test. 

For the lowest point supposing you are going to 
make that zero, short circuit your "unknown ' 
binding posts with a piece of thick wire and go 
through the same operation as above. When you 
have both lowest and highest points satisfactorily 
located, place a piece of cardboard along on the 
raised piece of wood where the slider index travels 
and mark the position of the index upon it at the 
highest and lowest resistance and divide up the 
space between into any convenient scale and paste 
the scale in place. The wire is probably not uni- 
form, and if you desire a greater degree of 
accuracy, it might be well to locate some of the 
intermediate points by placing the corresponding 
resistances between the binding posts and fixing 
the points that way. If well made this is a very 
serviceable bridge, and after a little practice in 
watching the light, you can quickly tell which way 



310 



ELECTKICITY AND ITS 




Figure ii. 



EECENT APPLICATIONS. 311 

to move the slider and how much. A glass shade 
over the galvanometer will improve its action 
somewhat by guarding against draughts of air. 

The Volt and Ammeter. These two instru- 
ments will be practically the same in everything 
except winding, so we will describe them together. 
The accompanying sectional elevation gives a good 
idea of the appearance of the instrument when 
completed. See Fig. n. One-half of it is 
removed for the sake of clearness. The form 




Figure 12. 

upon which the coil is wound can be made of 
wood, but a light casting of brass turned up makes 
a much neater and more substantial job. Make 
it so that the channel in which the wire is wound 
is Y\ r wide and y^ u deep and the diameter of the 
aperture in the centre 3^ ". See Fig. 12. 

This must be carefully insulated on the inside, 
especially in the case of the voltmeter. Wind the 
voltmeter with No. 34 German silver wire. The 
inside should be soldered to a thicker piece of 
copper wire which can pass through the bottom of 



ELECTRICITY AND ITS 



the ring by a hole in which is placed a wooden 
plug to insulate it. This winding will be suitable 
for measurements up to 150 volts. For higher 
voltages than this a smaller wire should be used. 
The winding of the ammeter will depend upon the 
current it is to measure. For currents up to 15 or 
20 amperes No. 10 copper wire would be about 
right. For heavier currents a copper strip should 
be used, insulated with mica or a silk ribbon. 
The ring when wound should be mounted on the 
base-board in a notched piece of wood and the 
wires led to suitable binding posts., 

A key should be placed in the voltmeter circuit 
in series with the coil. The coil when mounted 
should have its centre about 6" above the base- 
board. Make the needle box of dry, well-seasoned 
wood, 5" square and \% u deep. One end must be 
removable to allow the glass cover to slide in and 
out, and at the other end an aperture must be 
made for a brass cover which carries the needle. 
At the removable end is placed the scale which is 
mounted on a block of wood cut to the segment of 
a circle, whose centre is the point of suspension of 
the needle. The brass cover which carries the 
needle is shown in Fig. 13. 

This cover slides in grooves in the rear of the 
box. It has mounted on it a brass pillar with a 
hole drilled through its centre and carrying a plug 
at the top, with a milled head, upon which the fibre 



KECENT APPLICATIONS. 



S13 



is wound. This fibre passes down through the 
middle of the pillar and fastens to the suspension 
nook of the needle. The needle is composed of 
lour small steel magnets made from a medium- 
sized sewing needle. Cut them about £/' long 



Filve. S:5jf><nSfon 




M*g> 



Figure 13, 



and harden and magnetize them strongly. Thrust 
them through a piece of elder pith parallel to each 
other, as shown above, being careful to have the 
same poles point the same way. 

The pointer is to be made of two pieces of split 
straw, stuck together at one end and bound to £ 
piece of pith at the other with fine silk, and with 



314 ELECTRICITY AND ITS 

a piece of straw in the middle to spread them 
apart. The two pieces of pith should now be 
strung upon a fine piece of brass wire which passes 
through them twice and has a loop left to fasten 
the fibre. They will thus be held from turning 
relatively to each other, but not so strongly that 
they may not be twisted a little by hand when 
adjustment is necessary. The suspension wire 
should pass as nearly as possible through the 
middle of the group of little magnets. Now hang 
up the needle and counter-balance it with sealing- 
wax until the pointer stands horizontally. The 
suspension fibre is best if made of a piece of cocoon 
silk, but you can split up a piece of silk thread 
and get one that will answer the purpose. It is 
remarkable how much a single fibre of silk will 
support, so don't be deterred from keeping up the 
splitting process because what you already have 
looks fine. Fasten one end of the fibre to the 
plug at the top of the pillar and pass it down 
through the hole and fasten the other end to 
the hook. This is often a tedious job but pa- 
tience will insure its success. Then place the 
cover with the needle in the box and turn the plug 
until the needle is lifted clear, and see that the end 
of the pointer is over the scale block. Of course 
looking down on it you see only the edge which 
enables you to take a very fine reading. 



RECENT APPLICATIONS. 



315 



The box itself must be mounted, as shown, on a 
block at one end, and a brass rod at the other, and 
must be at such a height that when the needle 
within swings clear, it will be on the continuation 
of the axis of the coil. On the brass rod is 
mounted a bar-magnet which is arranged so it can 
be slid up and down, and clamped in any position 




Figure 14. 



with a set screw. This magnet must be made of 
the best steel and glass hard. It should be 
magnetized rather strongly and then "aged" by 
tapping it and immersing it for some hours in 
boiling water. This will reduce its strength but 
make it constant. The scale is marked off in 
tangents. This means that you lay off a circle on 
your scale paper equal to the radius of your 
pointer and draw a tangent to it. Beginning at 
the point of contact with the circle divide the 



316 ELECTRICITY AND ITS 

tangent into equal divisions, say io" to % ir and 
from these division points draw radial lines to the 
centre of the circle. Where these lines cut the 
circle they are to be marked and these divisions 
used as the scale. See Fig. 14. 

Three leveling screws must be put into the base- 
board, and it would be well tc hang a miniature 
plumb bob from the box and place a point beneath 
it on the base-board in such a position that when 
the bob is directly over it the fibre will swing free 
m the pillar. 

The calibration of these instruments will per- 
haps be the most difficult part of the work for the 
average amateur. The best method of course 
would be by the use of a Clark's cell and a poten- 
tiometer for the voltmeter, and the cell or a copper 
voltameter for the ammeter. 

Persons possessing this and the auxiliary appa- 
ratus will know, generally, how to use it, so that 
as a clear description of the process would take 
considerable space, we think it would be super- 
fluous here. Direct comparison with some stand- 
ard instrument we think will offer less difficulty 
than any other method supposing a reliable one tc 
be accessible, and will give results accurate enough 
for most work, it being understood, as we said at 
the beginning, that any considerable degree of 
accuracy is not to be expected with these instru- 
ments. These instruments are not very portable 



RECENT APPLICATIONS. 317 

and should be calibrated in the place where they 
are to be used. They should be placed upon a good 
solid table, or pier, and in a place where there is 
no movable iron about. Iron itself is not an objec- 
tion if it is stationary. The place should be at a 
distance from large currents or magnets. Set up 
the instrument on the table and carefully level it. 
Its coil should lie in the magnetic meridian and 
the controlling magnet with its south seeking pole 
to the north. Adjust the magnet so the needle 
points to zero on the scale and connect up the 
instrument to the source of current with your 
standard. Pass a current through them both and 
note the deflection ; then reverse the current 
through your instrument but not through the 
standard, and by the aid of your standard bring it 
to the same strength again. Note the deflection 
again, and if it be not the same it shows that your 
pointer is not at right angles to the needle mag- 
nets, and that they must be twisted relatively to 
each other. Do this, adjust to zero again with the 
controlling magnet and repeat the operation until 
with the same current as indicated by your stand- 
ard, the deflection to the right and left is equal. 
Now pass an even number of volts or amperes 
through your instruments and raise or lower your 
controlling magnet until the pointer is at a posi- 
tion on the scale that will give an even number of 
divisions of your scale per unit of current, say one 



318 ELECTRICITY AND ITS 

volt or ampere per division, five volts per division, 
etc. Take off the current and see if the pointer 
comes to zero ; if not, adjust it so it will and make 
another trial to get the magnet where it will give 
an even reading on the scale. When this position 
is finally found, mark the place on the rod support- 
ing the magnet and then find two or three other 
places which will give even readings. By having 
these you may vary the sensibility of your instru- 
ment to a large degree, according to the current 
vou wish to measure. 

We will close with a few directions as to the 
care of the instruments. After they are once in 
position and calibrated, do not disturb them or 
jar the magnets. If they were moved carefully 
and placed in the magnetic meridian, as before, in 
a place where H has the same value, they would 
read correctly, but this is not always easy to deter- 
mine, so they had better not be moved unless 
necessary. Do not keep the current on the 
voltmeter any longer than is necessary to take a 
reading, as the coil will become warm and will not 
give the same result as before. Temperature does 
not make any difference in the ammeter, so long 
as it does not get high enough to injure the insu- 
lation. The wires leading from the ammeter 
should be twisted together to prevent their influ- 
encing the instrument. Recalibration should be 
resorted to at short periods until you find that the 



RECENT APPLICATIONS. 



319 



controlling magnet has settled to the strength 
where it is going to stay. 

In the accompanying cuts are illustrated a 
number of electrical testing and measuring instru- 
ments for the use of schools and students begin- 
ning laboratory work. Electrical science has 
made such rapid advances that untrained skill is 
no longer of much avail, nor have the colleges 
themselves been able to properly do all that is 




Fig. 15. 

required of them in keeping up and at the head of 
investigation, while, at the same time, attempting 
to give elementary instruction. As a consequence 
each year more of this elementary work is rele- 
gated to the high schools and preparatory institu- 



320 



ELECTRICITY AND ITS 



tions. Most of these schools however, supported 
by municipalities, or by private endowment, are 
unable to purchase high grade testing instruments, 
even were it desirable to put such extremely 
delicate instruments in the hands of beginners. It 
is, claimed for the instruments shown that while 
capable of doing accurate work they are especially 




Fig. i 6. 

adapted to the use of beginners, as they are 
strongly made and have their delicate parts so 
arranged as to be easily and quickly replaced in 
case of injury. 

Fig. 15 shows a reflecting galvanometer of the 
Thomson type ; a small brass cylinder with glass 
face may be pushed backward and forward in the 
central axis of the coils, thus altering the size of 
the air chamber in which the mirror swings, and 



EEOEXT APPLICATIONS. 



321 



enabling the deflections to be made dead beat. 
In the Edelmann type, shown in Fig. 16, the 
mirror is attached to a bell magnet moving in a 
mass of copper ; by removing this mass of copper 
the instrument is made ballistic, thus making it 
useful for measurements of condenser capacities, 
battery resistances, comparison of electro-motive 
forces, etc. The coils are readily removable, as 
seen by the illustration, and may be changed in a 
moment for others of a higher or lower resistance. 




Fig. 17. 

Fig. 17 is one of four or five resistance boxes of 
this series. The instrument shown in the cut is a 
combination Wheatstone bridge and resistance set, 
having 12 coils in the resistance portion aggrega- 
ting 1,100 ohms, and bridge arms of 10,000 and 
1. 000 ohms on a side, thus giving a range of 
measurement from 1-100 ohms to 111,000. 



322 



ELECTRICITY AND ITS 



There is also a reading telescope, Fig. 18. The 
base is of cherry and supports a central rod of the 
same wood. On the central rod are two rings 
which can be raised, lowered or rotated on the rod, 
while they may be securely fastened in any posi- 
tion by means of a set-screw in the lower ring. 




Fig. 18. 



The upper ring carries the telescope and has a 
little lug held against a second set-screw in the 
lower one. By turning this set-screw a "fine" 
adjustment of the telescope in azimuth is secured. 
A set-screw in the upper ring allows the telescope 
to be adjusted in altitude. The instruments are 
placed on the market by Queen & Co., Philadelphia. 



RECENT APPLICATIONS. 323 

Horizontal Galvanometer, for measuring electri- 
cal resistances, testing currents, etc. Consists of 
a light magnetic needle, with agate bearings 
delicately pivoted on a needle-point, so as to have 
very little friction, and suspended above a flat coil 




HORIZONTAL GALVANOMETER. 



of wire. As an electric current passes through the 
coil, the needle is deflected out of the plane of the 
coil over a scale, and indicating by the amount of 
its deflection the intensity of the current. 

Cardew Voltmeter — This instrument differs 
from the greater number of voltmeters usually 
employed, in that it makes use of the heating effect 
of a current instead of its magnetic effect, and the 
rise of temperature of the conductor is measured 
by its expansion. This conductor, in the Cardew 
voltmeter, consists of about fourteen feet of plati- 
num-silver wire of extremely small diameter ; this 



;>24 



ELECTKICITY AND ITS 



wire is made to pass along the whole length of the 
instrument over several pulleys, one of which is 
movable, and back to a terminal near its beginning. 
The strain of the wire on this movable pulley is 




CARDEW VOLTMETER. 



counteracted by a cord attached to a spiral spring, 
and passing about a small wheel, which, by its 
revolution, causes the pointer to be carried over 
the scale. This, as the wire expands or contracts, 
the pointer indicates, by its greater or less deflec- 



RECENT APPLICATIONS. 



325 



tion, the amounts of such change. The advantage 
in using such a long, fine wire, in preference to a 
shorter one of much greater sectional area, is that 
the fine wire heats and cools much more quickly 




wheatstone's bridge. 

than the large one does, thus making the instru- 
ment nearly dead heat. By introducing extra 
resistance, a much greater range of electro-motive 
force can be used. 

The Cardevv voltmeter can be used equally well 
for direct or alternating currents, since, depending 



326 



ELECTRICITY AND ITS 



only on heating effect, errors of self-induction are 
not met with. 

The Wheatstone s Bridge, illustrated, is for 
measuring resistance, and consists of a wooden 




AYRTON & PERRY SPRING VOLTMETER AND SPRING AMMETER. 



box containing coils of insulated platinum-silver 
wire, so wound as to avoid self-induction. The 
coils are made of different sizes of wire, in order to 
vary their resistance from one to 4,000 ohms, and 



PvECEXT APPLICATIONS. 327 

their ends are connected to the brass blocks seen 
on the top of the box. A brass plug fits between 
each two adjacent blocks, and when it is in, it 
short circuits the coil, whose ends are attached to 
the blocks. It is by putting in or pulling out these 
plugs that the resistance in the circuit is varied, 
in order to make the desired measurement. 

The Ayrton & Perry Spring Voltmeter and 
Spring Ammeter are constructed on the same 
principle. Current is passed through a solenoid 
which then has a tendency to suck in any mag- 
netic object. A piece of iron is suspended in the 
solenoid by means of a peculiarly constructed 
spring, which, when the iron is drawn down by 
the action of the current, causes a pointer to 
move over a scale graduated to read directly in 
volts or amperes. The illustration is an ammeter ; 
the only difference between that and the volt- 
meter being in the size of wire used in the sole- 
noid. 



32$ 



ELECTRICITY AND ITS 



CHAPTER XXIII. 



Table of Different Ganges, with their Diameters and Areas in Mils. 



STANDARD 


. 


AMERICAN 




BIRMINGHAM. 


No of 


Diameter 


Area in 


No. of 


Diameter 


Area in 


No. of 


Diameter 




Gauge. 


in .Mile. 


CM=d« 


Gauge. 


in Mils. 


CM=d2 


Gauge. 


in Mils. 


CM=d* 


7-0 


500 


250000 














6-0 


464 


215296 


4-0 


4600 


211600 


4-0 


454 


206116 


5-0 


432 


186824 








3-0 


425 


180625 


4-0 


400 


160000 


3-0 


4096 


167805 








S-0 


372 


138384 


2-0 


3648 


133079 


2-0 


380 


144400 


2-0 


348 


121104 











340 


1156U0 





324 


104976 





3249 


105592 








1 


300 


90000 








1 


300 


90000 


2 


276 


76176 


1 


2893 


83694 


2 


284 


80656 


3 


252 


63504 


2 


2576 


66373 


8 


259 


67081 


4 


232 


63824 


3 


2294 


62634 


4 


288 


56644 


6 


212 


44944 








5 


220 


48400 


6 


192 


36864 


4 


2043 


41742 


6 


203 


41209 


7 


176 


30976 


5 


1819 


83x02 


7 


180 


32400 


8 


160 


25600 


6 


162 


26244 


8 


165 


27225 


9 


144 


20736 


7 


1443 


20822 


9 


148 


21904 


10 


128 


16384 


8 


1286 


16512 


10 


134 


179fG 



Table of Different Gauges, with their Diameters and Areas in Mils, 



STANDARD. 


AMERICAN. 


BIRMINGHAM. 


No. of 


Diameter 


Area in 


No. of 


Diameter 


Area in 


No. of 


Diameter 


Area rn 


Gauge. 


in Mile. 


CM=d« 


Gauge. 


in Mils. 


CM=d* 


Gauge. 


Id Mils. 


CM=d» 


11 


118 


13456 


9 


1144 


13110 


11 


120 


14400 


12 


104 


10816 


10 


1019 


10381 


12 


109 


11881 


13 


092 


8464 


11 


0907 


8226 


13 


095 


9025 


14 


080 


6400 


12 


0808 


6528 


14 


083 


6889 


15 


072 


6184 


13 


072 


5184 


15 


072 


5184 


16 


064 


4096 


14 


0641 


4110 


16 


065 


4225 


17 


056 


8136 


15 


0571 


3260 


17 


068 


3364 


18 


048 


2304 


16 


0508 


2581 


18 


049 


2401 








17 


0152 


2044 


19 


042 


1764 


19 


040 


1600 


18 


0403 


1624 








20 


036 


1296 


19 


0359 


1253 


20 


035 


1225 


21 


032 


1024 


20 


032 


1024 


21 


032 


1024 


22 


028 


784 


21 


0285 


8-'0 


22 


028 


784 


23 


024 


576 


22 


0253 


626 


23 


025 


625 


24 


022 


484 


23 


0226 


610 


24 


022 


484 


25 


020 


400 


24 


0201 


404 


25 


020 


400 


96 


018 


924 


25 


6179 


820 


1 26 


018 


tm 



RECENT APPLICATIONS. 



329 



TABLE SHOWING THE DIFFERENCE BETWEEN WIRE GAUGES. 



No. 

0000 

000 

00 

0. 

1 . 

2 . 
3. 
4. 

5 . 

6 . 
7. 

8 . 

9 . 
10, 
11 . 
12. 
13 . 
14. 
15.* 
16. 
17. 
18. 
i9. 
20. 
21 . 
22. 
23 . 
24. 
25 . 
26. 
27. 

28 . 

29 . 
30. 
31 . 
32. 
33 . 
34. 
35. 



New 












British. London,, Stubs' 1 


.400 . . . . .454 . . . 


. .454 


.372 . . 




. .425 . 




. .425 


.348 . 






. .380 . 




. .380 


.324 . 






.340 . 




. .340 


.300 . 






.300 . 




. .300 


.276 . 






. .284 . 




. .284 


.252 . 






.259 . 




. .259 


.232 . 






.238 . 




. .238 


.212 . 






.220 . 




. .220 


.193 . 






.203 . 




. .203 


.176. 






.180. 




. .180 


.160 . 






.165 . 




. .165 


.144 . 






.148 . 




. .148 


.128 . 






.134. 




. .134 


.116 . 






.120 . 




. .120 


.104 . . 






.109 . 




. .109 


.092 . 






.095 . , 




. .095 


.080 . . 






.083 . 




. .083 


.072 . . 






.072 . . 




. .072 


.064. . 






.065 . . 




. .065 


.056 . . 






.058 . 




. .058 


.048 . . 






.049 . . 




. .049 . 


.040 . . 






.040 . . 




. .042 


.036 . . 






.035 . 




. .035 . 


.032 . . 






.0315 




. .032 . 


.028 . . 






.0295 




. .028 . 


.024 . . 






.027 . . 




. .025 . 


.022 . . 






.025 . . 




. .022 


.020 . . 






.023 . . 




. .023 


.018 . . 






.0105 . 




. .018 . 


.0164 . 






.01875 . 




. .016 . 


.0148 . 






.0165 . 




. .014 . 


.0136 






.0155 . 




. .013 . 


.0124 . 






.01375 . 




. .012 . 


.0116 . 






.01225 . 




. .010 . 


.0108 






.01125 . 




. .009 . 


.0100 . 






.01025 . 




. .008 . 


.0092 . 






.0095 . 




. .007 . 


.0084 . 






.009 , . 




. .005 . 


.0075 , 






.0075 . 




. .004 , 



Brown & 
Sharpens. 
.460 
.40964 
.36480 
.32495 
.28930 
.25763 
.22942 
.20431 
.18194 
.16202 
.14428 
.12849 
.11443 
.10189 
.09074 
.08081 
.07196 
.06408 
.05706 
' .05082 
.04525 
.04030 
.03589 
.03196 
.02846 
.025347 
.022571 
.0201 
.0179 
.01594 
.014195 
.012641 
.011257 
.010025 
.008928 
.00795 
.00708 
.0063 
.00561 
.005 



330 



ELECTRICITY AND ITS RECENT APPLICATIONS, 



RESISTANCE AND WEIGHT TABLE, 

For Cotton and Silk Covered and Bare Copper Wire. 



AMERICAN GAUGE. 



The resistances are calculated for pure copper wire. The wire 
is about 98 per cent, of the conductivity of pure copper. 

The number of feet to the pound is only approximate for insul- 
ated wire. 





- 

FEET PER POUND. 


RESISTANCE, NAKED COPPER. 


"NT/-. 


Cotton 


Silk 


Naked. 


Ohms per 


Ohms 


Feet 


Ohms 


IN O. 


covered. 


covered. 


1000 feet. 


per mile. 


per ohm. 


per pound. 


8 






20 


.6259 


3-3 


1600. 


.0125 


9 






2 $ 


7892 


4.1 


j -72. 


.0197 


10 






32 


.8441 


A.4 


118*. 


.0270 


11 






40 


1.254 


6.4 


798. 


.0501 


12 


42 


46 


50 


1.580 


8-3 


633. 


•079 


13 


re 


6c 


H 


- 995 


10.4 


5^4- 


.I2T 


14 


. 68 


75 


80 


2 504 


1 ?.". 


40c, 


.200 


J 5 


8? 


95 


IOI 


3.172 


16.7 


316. 


.320 


16 


no 


120 


128 


4.001 


23. 


230. 


.512 


17 


140 


*5° 


161 


5-o4 


26. 


198. 


.8ll 


18 


175 


190 


203 


6.36 


33- 


157- 


1.29 


19 


220 


240 


256 


8.25 


43- 


121. 


2. II 


20 


280 


305 


324 


10. 12 


53- 


99. 


3-27 


21 


360 


39° 


408 


12.76 


68. 


76.5 


• 5-20 


22 


45o 


490 


514 


16.25 


85. 


61.8 


8.35 


23 


560 


615 


649 


20.30 


108. 


48.9 


13 -3 


24 


715 


775 


818 


25.60 


135- 


39-° 


20.9 


25 


910 


990 


1030 


32.2 


170. 


31.0 


33-2 


26 


1165 


1265 


1300 


40.7 


214. 


24.6 


52-9 


27 


1445 


157° 


1640 


5i-3 


270. 


19-5 


84.2 


28 


1810 


1970 


2070 


64.8 


343- 


15-4 


134. 


29 


2280 


2480 


2617 


81.6 


432. . 


12.2 


213. 


30 


2805 


3050 


3287 


103. 


538. 


9.8 


338. 


31 


3605 


3920 


4144 


130. 


685. 


7-7 


539- 


32 


4535 


4930 


5227 


164. 


865. 


6.1 


856. 


33 




6200 


6590 


206. 


1033- 


4.9 


1357- 


34 




7830 


8330 


260. 


1389. 


3-8 


2166. 


35 




9830 


10460 


328. 


1820. 


2.9 


352i. 


36 




12420 


13210 


414. 


2200. 


2.4 


5469- 



ILLUSTRATED DICTIONARY 

OF 

ELECTRICAL TERMS 

AND PHRASES. 



ELECTPvICITY AND ITS RECEST APPLICATIONS. 335 



CHAPTER XXIV. 

ACCUMULATOR. — See battery and condenser. 
AMMETER. — An instrument for measuring 
current strength. 

AMPERE. —The unit of current strength. It is 
the flow of electricity produced by the pressure 
of one volt on the resistance of one ohm. 

ANODE. — The conductor or plate of a decompo- 
sition cell connected with the positive terminal 
of any electric source. The term usually used 
to designate terminal of a source at which 
electrolysis is taking place. It is the plate con- 
nected with the positive terminal, which is dis- 
solved in the process of electro plating. 

ARC. — The stream of hot gasses and particles of 
carbon visible between the carbons of an arc 
lamp. 

ARMATURE. — That part of a dynamo in which 
the current is induced. It may be a stationary 
or moving part, but is generally the latter, and is 
composed of coils of wire which " cut " the lines 
of magnetic force produced by the fields. This 
" cutting " induces a current in the coils. 



336 



ELECTRICITY AND ITS 



ARMATURE CORE.— The core of iron of a 
dynamo or motor around or on which the coils 
of wire are wound or disposed. 




BATTERY. — One or more cells in which elec- 
tricity is produced by chemical action. There 
are two elements of different substances and a 
liquid in every voltaic battery. A primary bat- 
tery is one in which the " elements " are placed 
and used until they are worn out. In a second- 
ary or storage battery or accumulator the " ele- 
ments " are placed in the cell and first "formed" 
by the passage of a current of electricity through 
them. The cell is then said to be charged and 
may be used to supply electricity. The term 
battery is also used to designate a collection of 
Leyden jars in which static electricity is stored. 

BRUSH. — A collection of .metal sheets or wires 
which press against the commutator of a dynamo 
to collect the electricity, or of a motor to supply 
it. Carbon brushes are coming into use now 
especially in railway work. 



KECEXT APPL.ICATIOM'S. 



337 



B. & S. — Brown and Sharp. The wire gauge 
used in America. 

B. W. G. — Birmingham wire gauge. The English 
wire gauge. 

CELL. — The jar in which the elements and 
liquid of a battery are placed. The term is 
used also for the jar and its contents. 




C. G. S. — The abbreviation of centimetre, 
gramme, second, and used to designate the so- 
called absolute system of measurements. 

CIRCUIT. — A system of conductors over which 
electricity passes. 

COIL, CLOSED. — The coils of an armature are 
said to be closed when the end of one is con- 
nected to the beginning of the next at the 
commutator bar. An open coil armature is one 

22 



388 ELECTRICITY AND ITS 

in which each coil is independent of the others 
and has its own commutator bars, 

COILS, RESISTANCE. — Coils of wire, the 
electrical resistance of which is known, em- 
ployed for measuring the resistance of a circuit. 




COMMUTATOR.— That part of a dynamo on 
which the current from the armature is rectified 
before passing to the external circuit. The cur- 
rent in a given section of an armature alternates 
and must be made continuous on leaving it. 
This is done by the commutator, which consists 
of a series of insulated metal bars connected to 
the armature wires and so placed as to feed into 
different brushes as the current changes. 

CONDENSER. — An apparatus for collecting 
and holding electricity. It consists of alternate 
layers of conducting sheets and insulating 
material, the conductors being very close to- 
gether, and the adjacent ones being charged 



RECENT APPLICATIONS. 339 

with the opposite kinds of electricity. Their 
proximity enables them to hold a larger amount 
of electricity than they could if alone. Condens- 
ers are sometimes called accumulators. 

CONDUCTOR. — A substance which will allow 
the passage of electricity over it. All sub- 
stances will do this, but some to so small an 
extent that they are called insulators. 

COULOMB. — The unit of electric quantity. It 
is the amount of electricity which flows past 
a given point in one second on a circuit convey- 
ing one ampere. 

CURRENT. — The flow of electricity in a con- 
ductor analogous to the flow of water in a pipe. 
A continuous current is one that does not 
change its direction, while the alternating cur- 
rent is one that periodically reverses. 

CUT OUT. — An arrangement for interrupting 
a current or for shunting it around some part 
of a circuit. 

DYNAMO. — A machine driven by power which 
furnishes electricity. 

DYNAMOMETER. — An apparatus for measur- 
ing the power given out or consumed by a 
machine. An electro-dynamometer is an instru- 
ment for measuring a current bv the mutual 
action of two coils through which it passes. 



340 ELECTRICITY AND ITS 

ELECTRODE. — A pole of a battery. 

E. M. F. — An abbreviation for electro-motive 
force. This is the pressure which forces the 
electric current through a conductor. 

ELECTRO-MAGNET.— A magnet produced by 
passing a current through a coil of wire around 
a soft iron core. The core is magnetized while 
the current flows, but loses its magnetism when 
the current stops. This form of magnet may be 
made much more powerful than a permanent 
magnet, and is therefore used in place of the 
latter in dynamos. 




FARAD. — The unit of capacity. A condenser 

that will hold one coulomb at a pressure of one 

volt has a capacity of one farad. 
FILAMENT. — In an incandescent lamp the 

thread of carbon which becomes luminous when 

the current is passed through it. 
FORMULAE. — Mathamatical expression for 

some general rule or principle, for example, in 

the formation of Ohms law 

C=E 
R. 



RECENT APPLICATIONS. 



341 



C, the current is equal to the electro-motor 
force — E, divided by the resistance R. For- 
mulae are usually written in the form of an 
equation and therefore contain the sign of 
equality or . = 
FOUCAULT CURRENTS. — Local, Eddy, or 
Parasitical — useless currents produced in 
metallic masses of the pole pieces, armatures or 
field magnet cores of dynamo electric machines 
or motors, either by motion of these parts 
through the magnetic fields, or by the variations 
in the strength of electric currents flowing near 
them. 

FRICTIONAL ELECTRICITY. — Electricity 
produced by friction, as by frictional machines, 
as the Holtz, Toppler, Holtz, etc. Is often 
produced by belts around pulleys. 

GALVANOMETER.— An instrument for de 
tecting and measuring the electric current by 
the action of a coil of wire upon a magnetic 
needle. 




642 



ELECTKICITY AND ITS 



INDUCTION.— A current is said to be induced in 
a conductor when it is caused by the conductor 
cutting lines of magnetic force. A fluctuating 
current in a conductor will tend to induce a 
fluctuating current in another running parallel 
to it. A static charge of electricity is induced 
in neighboring bodies by the presence of an 
electrified body. A magnet " induces" magnet- 
ism in neighboring magnetic bodies. 

INDUCTION COIL.— An arrangement by which 
an alternating or fluctuating current in a coil of 
wire will induce an alternating current in a par- 
allel coil. 




KATHODE. — The name given to the plate at- 
tached to the negative terminal of an electric 
source, generally used in connection with elec- 
trolysis. The article undergoing the process of 
electro-plating may be termed a Kathode. 

LINES OF FORCE. — Imaginary lines which 
radiate from a magnet and show by their direc- 
tion the path which a free magnetic pole would 
take if left to itself. Conventionally the strength 
of a magnetic field is indicated by the number of 



RECENT APPLICATIONS. 343 

these lines. Their form is shown by the well 
known experiment with the magnet and iron 
filings. 
MAGNET. — A body possessing the property of 
attracting iron, steel and a few other metals. 

MAGNETIC FIELD. — The space around a mag- 
net in which its power of attraction is exhibited. 

MULTIPLE or MULTIPLE ARC.— A method 
of connecting electric conductors by which a 
number of sources of electricity feed directly into 
or a number of receivers of electricity take it 
directly from the same mains. 

NEGATIVE. — A conventional term to indicate 
the direction of flow of a current, or the state ot 
electrification of a body. The negative or ter- 
minal of a dynamo is the one at which electricity 
enters it from the external circuit, while the 
negative terminal of a lamp or instrument is that 
connected towards the negative terminal of a 
dynamo. It is designated by — 

OHM. — The unit of electrical resistance. 

OHMS LAW. — States that the current in any 
circuit is equal to the E. M. F. acting on it divi- 
ded by its resistance. 

PERMANENT MAGNET.— A piece of hard- 
ened steel which retains its magnetism after the 
magnetizing influence is removed. 

PARALLEL.— See Multiple. 



344 ELECTRICITY AXD ITS 

POLE — Those parts of a magnet which show the 
strongest magnetic force. In a bar magnet this 
is generally a short distance from the ends. The 
pole cf a dynamo or battery is one of its termi- 
nals. 

POSITIVE. — -A conventional term to show the 
direction of a current. In a dynamo or battery 
it is the terminal at which the electricity leaves 
it. It is designated by -|-. 

POTENTIAL. — Power to do work. It is com- 
monly used as synonymous with electro-motive 
force in speaking of dynamos or batteries. 

RESISTANCE. — The opposition offered by a 
body to the passage of electricity through it. 

RHEOSTAT. — An apparatus for throwing a vari- 
able resistance into a circuit at will. 

SERIES. — Two or more conductors are said to be 
in series when they are so connected that the 
same current that passes through one passes 
through the other. 

SHORT CIRCUIT.— An indefinite term, used 
generally in the case of dynamos and batteries 
for a resistance between the terminals lower 
than the machine or battery is calculated to 
stand or run on in practice. With lamps the 
term is used for a low resistance between the 
terminals, which deprives it of most of the cur- 
rent. 



RECENT APPLICATIONS. 



34a 



SHUNT. — A shunt is a conductor connected 
around another in such a way that it deprives the 
first of a part of the current. 

SOLENOID.— A hollow coil of wire. 

TERMINAL. — The point at which the electricity 
enters or leaves an electrical apparatus. 

THERMO-ELECTRICITY. — Electricity pro- 
duced by differences of temperature at the 
junctions of dissimilar metals. It may even be 
produced in the same metal ; such as a wire 
part of which is straight and the remainder bent 
into a spiral, if heated at one end by the flame 
of a lamp. 

VACUUM. — A space from which all traces of 
residual gas or gases have been removed. 

VENTILATING ARMATURE.— An armature 
so constructed that it draws a current of air 
from both ends and along the line of shaft and 
out through the discs, which are separated, and 




j ¥1 * 



346 ELECTRICITY AND ITS RECENT APPLICATIONS. 

through the winding, with openings to let the 
air pass out. The rapid rotary motion of the 
armature sends out the current of air, which 
keeps the armature and pole pieces cool and 
therefore more effective than the old style 
which is so liable to heat up. 

VOLT. — The unit of electro-motive force or pres- 
sure analogous to the head of water in hydraulics. 

VOLTAMETER — An electrolytic cell employed 
for measuring the strength of the electric cur- 
rent passing through it by the amount of 
chemical decomposition effected in a given 
time. 

VOLTMETER. — An instrument for measuring 
the voltage or pressure on a circuit. 

WATT. — The unit of work. The watts developed 
in a circuit are equal to the current multiplied by 
the E. M. F. 746 watts equal one horse power. 

WATTMETER. — An instrument for measuring 
the electrical energy in a circuit. 



APPENDIX, 



AUTOMOBILES. 

That the horseless carriage has come to stay no 
one denies. There are three varieties, the electric, 
the gasoline, and the steam. In this chapter we 
shall describe the electric only, and for examples 
have selected types of the Waverley. 

The vehicles described herein are the very latest 
additions to the Waverley Line, and vary in con- 
struction in several ways from any vehicles yet pro- 
duced by them, being lighter, and of longer range, 
than any now on the market. With these models 
they hope to meet the popular and growing demand 
for a light, comfortable and handsome vehicle at a 
low price to the purchaser ; and we believe an ex- 
amination and inspection of these vehicles will be 
convincing proof that they have succeeded, without 
reducing the high mechanical standard of their 
products. 

To the electric carriage, as compared with any 
other motive power, the following points of supe- 
riority are conceded : 



348 



APPENDIX, 




MODEL NO. 21. ROAD WAGON. WEIGHT IOOO LBS. 



APPENDIX. 349 

It is safe, simple in operation, noiseless, odorless, 
clean, efficient, economical, comfortable, handsome, 
and durable. The exclusive possession of all these 
qualities places the Waverley vehicle in a class by 
itself — unapproachable, incomparable. The pleas- 
ure of electrical operation and riding is complete, 
as it is free from the nervous strain which must ac- 
company the attendance of complicated mechanism. 
In the Waverley Electric Carriage is realized the 
satisfaction of repose in action. 

A description of Model No. 21 is as follows : 

Piano box pattern: length, 5 feet 10 inches; 
width, 2 feet 3 inches ; height from ground, 25 
inches. 

The wheels are 30 inches in diameter, wire 
spokes ; 2^-inch pneumatic tires. 

The motor is of a new and improved design, of a 
normal capacity of 2 H. P., capable of an overload 
of 2 H. P. additional. Speed from 5 to 17 miles 
per hour. 

The gearing is of the " herring-bone " type, pro- 
tected in dust-proof cases and runs in oil. 

Each vehicle is equipped with a combination volt 
and ammeter. 

The storage battery is used. Weight, 360 
pounds. 

A rheostat is used for charging the batterv. 

Model No. 22 is a piano box pattern ; length, 



350 



APPENDIX. 




MODEL NO. 22. ROAD WAGON, WITH TOP. WEIGHT IO50 LBS 



APPENDIX. 351 

5 feet 10 inches; width, 2 feet 3 inches; height 
from ground, 25 inches. 

It has a full leather top. 

The wheels are 30 inches diameter, wire spokes ; 
2j-inch pneumatic tires. 

The motor is of a new and improved design, of a 
normal capacity of 2 H. P., capable of an overload of 
2 H. P. additional. Speed, from 5 to 17 miles per 
hour. 

The gearing is of the " herring-bone " type, pro- 
tected in dust-proof cases, and runs in oil. 

Each vehicle is equipped with a combination volt 
and ammeter. 

The storage battery is used, and is described on 
page 12. Weight, 360 pounds. 

A rheostat is used for charging battery — the 
same as in Model 21. 




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